Research Line:

Water and extremes

This research line studies extreme hydrometeorological events and their impact on society and ecosystems, both natural and non-natural, analyzing the roles played by natural variability and anthropogenic climate change.

For the 2024-2025 period, the line aims to deepen the characterization of extreme events and their socio-environmental impacts, especially heat waves, mega-fires, and hyper-droughts, by evaluating their natural and anthropogenic drivers, projecting their future occurrence and formally attributing human-induced climate change to such impacts.

Simultaneously, it proposes to determine how climate change, natural climate variability, and increasing water demand affect water security in central-southern Chile. Additionally, it seeks to evaluate the ranges of hydrological memory, the main hydroclimatic characteristics and processes that control it, and how the propagation of extreme precipitation events is modulated under warmer climatic conditions.

Work is also being done to characterize the dynamics and interconnections of crucial aspects that determine the regional hydroclimate in Chile, which currently present signals of climate change alteration, such as the strengthening of the South Pacific Anticyclone, the strengthening and southward migration of the westerly winds, patterns of atmospheric blocking in the Southern Ocean and Antarctica, and the temporal stability between El Niño-Southern Oscillation (ENSO) and the precipitation regime in central Chile.

Review the research achievements of this line in our institutional report.






Related publications

TítuloAutoresLínea de InvestigaciónAñoDOIAbstractRevistaISSNAccesoPáginasVolumenIndexKey Words
The role of climate and disturbance regimes upon temperate rainforests during the Holocene: A stratigraphic perspective from Lago Fonk (∼40°S), northwestern PatagoniaHenríquez, Carla A.; Moreno, Patricio I.; Lambert, Fabrice; Alloway, Brent V.Ciudades Resilientes; Agua y Extremos2021.010.1016/j.quascirev.2021.106890Quaternary Science Reviews02773791 Reuters ISIcharcoal, explosives, fires, forestry, stratigraphy, volcanoes, centennial/millennial-scale variability, climate regime, disturbance regime, explosive volcanism, fire disturbance, holocenes, lake sediment cores, patagonia, pollen analysis, temperate rainforest, lakes, charcoal, climate variation, disturbance, explosive volcanism, fossil record, holocene, rainforest, stratigraphy, temperate forest, vegetation dynamics, chile, cumbria, england, lake district, longitudinal valley, patagonia, taiwan, united kingdom, eucryphia
Hydrological droughts in the southern Andes (40–45°S) from an ensemble experiment using CMIP5 and CMIP6 modelsAguayo, Rodrigo; León-Muñoz, Jorge; Garreaud, René; Montecinos, AldoAgua y Extremos2021.010.1038/s41598-021-84807-4Abstract The decrease in freshwater input to the coastal system of the Southern Andes (40–45°S) during the last decades has altered the physicochemical characteristics of the coastal water column, causing significant environmental, social and economic consequences. Considering these impacts, the objectives were to analyze historical severe droughts and their climate drivers, and to evaluate the hydrological impacts of climate change in the intermediate future (2040–2070). Hydrological modelling was performed in the Puelo River basin (41°S) using the Water Evaluation and Planning (WEAP) model. The hydrological response and its uncertainty were compared using different combinations of CMIP projects (n = 2), climate models (n = 5), scenarios (n = 3) and univariate statistical downscaling methods (n = 3). The 90 scenarios projected increases in the duration, hydrological deficit and frequency of severe droughts of varying duration (1 to 6 months). The three downscaling methodologies converged to similar results, with no significant differences between them. In contrast, the hydroclimatic projections obtained with the CMIP6 and CMIP5 models found significant climatic (greater trends in summer and autumn) and hydrological (longer droughts) differences. It is recommended that future climate impact assessments adapt the new simulations as more CMIP6 models become available.Scientific Reports2045-2322 Reuters ISI
A review of the observed air temperature in the Antarctic Peninsula. Did the warming trend come back after the early 21st hiatus?Carrasco, Jorge F.; Bozkurt, Deniz; Cordero, Raul R.Zonas Costeras; Agua y Extremos2021.010.1016/j.polar.2021.100653Recent changes in the near-surface air temperature (nSAT) in the Antarctic Peninsula (AP) suggests that the absence of 21st century warming on Antarctic Peninsula may be coming to end. To examine this, the long-term annual and seasonal variability of the nSAT at eight Antarctic stations located in the AP are analyzed using available data from the SCAR Reader database, complemented with data from the Chilean Weather Service (Frei and O’Higgins). An exponential lter was applied to the original annual and seasonal mean series to obtain a decadal-like variation of the nSAT. A stacked and the standardized anomaly of the nSAT record was constructed to examine the average regional behavior in the AP. Cumulative sum (CUSUM) and changepoint analysis were applied through the stacked nSAT series to highlight signi cant changes caused by variation in weather and climate. The CUSUM and bootstrapping analysis revealed two statistically signi cant breaking points during the 1978–2020 period. The rst one occurred in the late nineties ending a warming period and making the beginning of a cooling period; the second one may have taken place in the mid-2010s and could mark the end of the warming pause. These trends appear to be consistent with the changes observed in the large-scale climate modes (i.e., the Antarctic Annular Mode – AAO).Polar Science18739652 Reuters ISIair temperature, antarctic peninsula, change point, reader database, warming and cooling trends
Disentangling the effect of future land use strategies and climate change on streamflow in a Mediterranean catchment dominated by tree plantationsGalleguillos, Mauricio; Gimeno, Fernando; Puelma, Cristóbal; Zambrano-Bigiarini, Mauricio; Lara, Antonio; Rojas, MaisaCambio de Uso de Suelo; Agua y Extremos; Gobernanza e Interfaz Ciencia y Política2021.010.1016/j.jhydrol.2021.126047Climate change (CC) along with Land Use and Land Cover Change (LULCC) have a strong influence in water availability in already fragile Mediterranean ecosystems. In this work the Soil and Water Assessment Tool (SWAT) was implemented for the 2006–2018 period in a rainfed catchment of central Chile (36°) to test the hypothesis that adaptive plantation strategies could mitigate the impacts of climate change and increase streamflow. We also hypothesize that afforestation with exotic tree plantations will reduce water availability in Mediterranean catchments, acting in synergy with climate change. Five LULCC scenarios are analyzed: i) current long-term national Forest Policy (FP), ii) extreme scenario (EX) with large afforestation surfaces, both including the replacement of native shrublands with Pinus radiata; iii) adaptive plantation management scenario (FM), with lower planting density, iv) forced land displacement scenario (FLD), where plantations at the headwaters are moved to lowland areas and replaced with native shrublands, and v) pristine scenario (PR), with only native vegetation. Each LULCC scenario was run with present climate and with projections of different CMIP5 climate models under the RCP 8.5 scenario for the period 2037–2050, and then compared against simulations based on the present land cover and climate. Simulations with the five LULCC scenarios (FP, EX, FM, FLD and PR) with present climate resulted in variations of −2.5, −17.3, 0, 2.3 and 10.9% on mean annual streamflow (Q), while simulations with the current land cover and CC projections produced a 32.1% decrease in mean annual Q. The joint impact of CC and LULCC leads to changes in mean annual Q ranging from −46.2% (EX) to –23.3% (PR). Afforestation with exotic pines will intensify the reduction in water yield, while conservative scenarios focused on native forests protection and restoration could partially mitigate the effect of CC. We make a strong call to rethink current and future land management strategies to cope with lower water availability in a drier future.Journal of Hydrology00221694 Reuters ISIcatchments, climate models, conservation, land use, reforestation, runoff, stream flow, land use and land cover change, land-use strategies, mediterranean catchment, mediterranean ecosystem, plantation managements, protection and restoration, soil and water assessment tool, water availability, climate change, afforestation, catchment, climate change, coniferous forest, coniferous tree, land cover, land use, land use change, shrubland, soil and water assessment tool, streamflow, tree planting, mediterranean region, pinus radiata
Radiocarbon bomb-peak signal in tree-rings from the tropical Andes register low latitude atmospheric dynamics in the Southern HemisphereAncapichún, Santiago; De Pol-Holz, Ricardo; Christie, Duncan A.; Santos, Guaciara M.; Collado-Fabbri, Silvana; Garreaud, René; Lambert, Fabrice; Orfanoz-Cheuquelaf, Andrea; Rojas, Maisa; Southon, John; Turnbull, Jocelyn C.; Creasman, Pearce PaulCiudades Resilientes; Agua y Extremos; Gobernanza e Interfaz Ciencia y Política2021.010.1016/j.scitotenv.2021.145126South American tropical climate is strongly related to the tropical low-pressure belt associated with the South American monsoon system. Despite its central societal role as a modulating agent of rainfall in tropical South America, its long-term dynamical variability is still poorly understood. Here we combine a new (and world's highest) tree-ring 14C record from the Altiplano plateau in the central Andes with other 14C records from the Southern Hemisphere during the second half of the 20th century in order to elucidate the latitudinal gradients associated with the dissemination of the bomb 14C signal. Our tree-ring 14C record faithfully captured the bomb signal of the 1960's with an excellent match to atmospheric 14C measured in New Zealand but with significant differences with a recent record from Southeast Brazil located at almost equal latitude. These results imply that the spreading of the bomb signal throughout the Southern Hemisphere was a complex process that depended on atmospheric dynamics and surface topography generating reversals on the expected north-south gradient in certain years. We applied air-parcel modeling based on climate data to disentangle their different geographical provenances and their preformed (reservoir affected) radiocarbon content. We found that air parcel trajectories arriving at the Altiplano during the bomb period were sourced i) from the boundary layer in contact with the Pacific Ocean (41%), ii) from the upper troposphere (air above the boundary layer, with no contact with oceanic or continental carbon reservoirs) (38%) and iii) from the Amazon basin (21%). Based on these results we estimated the ∆14C endmember values for the different carbon reservoirs affecting our record which suggest that the Amazon basin biospheric 14C isoflux could have been reversed from negative to positive as early as the beginning of the 1970's. This would imply a much faster carbon turnover rate in the Amazon than previously modelled.Science of The Total Environment00489697 Reuters ISIboundary layers, carbon, forestry, topography, tropics, atmospheric dynamics, carbon reservoirs, continental carbons, geographical provenances, latitudinal gradients, southern hemisphere, tropical climates, upper troposphere, bombs (ordnance), carbon 14, atmospheric circulation, atmospheric dynamics, atmospheric modeling, carbon isotope, latitudinal gradient, paleoclimate, radiocarbon dating, southern hemisphere, tree ring, amazonas (brazil), araucaria, araucaria angustifolia, article, atmosphere, atmospheric circulation, bomb, bomb signal, carbon reservoir effect, chile, controlled study, environmental impact, environmental parameters, geographic distribution, latitude, new zealand, nonhuman, pacific ocean, plant structures, polylepis tarapacana, priority journal, rosaceae, southern hemisphere, surface topography, topography, tree ring, troposphere, turnover rate, bomb, brazil, sea, tree, amazon basin, andes, brazil, new zealand, pacific ocean, bombs, brazil, oceans and seas, pacific ocean, trees
Temperature and precipitation projections for the Antarctic Peninsula over the next two decades: contrasting global and regional climate model simulationsBozkurt, Deniz; Bromwich, David H.; Carrasco, Jorge; Rondanelli, RobertoZonas Costeras; Agua y Extremos2021.010.1007/s00382-021-05667-2This study presents near future (2020–2044) temperature and precipitation changes over the Antarctic Peninsula under the high-emission scenario (RCP8.5). We make use of historical and projected simulations from 19 global climate models (GCMs) participating in Coupled Model Intercomparison Project phase 5 (CMIP5). We compare and contrast GCMs projections with two groups of regional climate model simulations (RCMs): (1) high resolution (15-km) simulations performed with Polar-WRF model forced with bias-corrected NCAR-CESM1 (NC-CORR) over the Antarctic Peninsula, (2) medium resolution (50-km) simulations of KNMI-RACMO21P forced with EC-EARTH (EC) obtained from the CORDEX-Antarctica. A further comparison of historical simulations (1981–2005) with respect to ERA5 reanalysis is also included for circulation patterns and near-surface temperature climatology. In general, both RCM boundary conditions represent well the main circulation patterns of the historical period. Nonetheless, there are important differences in projections such as a notable deepening and weakening of the Amundsen Sea Low in EC and NC-CORR, respectively. Mean annual near-surface temperatures are projected to increase by about 0.5–1.5 ∘C across the entire peninsula. Temperature increase is more substantial in autumn and winter (∼ 2 ∘C). Following opposite circulation pattern changes, both EC and NC-CORR exhibit different warming rates, indicating a possible continuation of natural decadal variability. Although generally showing similar temperature changes, RCM projections show less warming and a smaller increase in melt days in the Larsen Ice Shelf compared to their respective driving fields. Regarding precipitation, there is a broad agreement among the simulations, indicating an increase in mean annual precipitation (∼ 5 to 10%). However, RCMs show some notable differences over the Larsen Ice Shelf where total precipitation decreases (for RACMO) and shows a small increase in rain frequency. We conclude that it seems still difficult to get consistent projections from GCMs for the Antarctic Peninsula as depicted in both RCM boundary conditions. In addition, dominant and common changes from the boundary conditions are largely evident in the RCM simulations. We argue that added value of RCM projections is driven by processes shaped by finer local details and different physics schemes that are introduced by RCMs, particularly over the Larsen Ice Shelf.Climate Dynamics0930-7575, 1432-0894 Reuters ISIair temperature, climate change, climate modeling, cmip, downscaling, extreme event, global climate, precipitation assessment, regional climate, antarctic peninsula, antarctica, larsen ice shelf, west antarctica
Mapping water ecosystem services: Evaluating InVEST model predictions in data scarce regionsBenra, F.; De Frutos, A.; Gaglio, M.; Álvarez-Garretón, C.; Felipe-Lucia, M.; Bonn, A.Agua y Extremos2021.010.1016/j.envsoft.2021.104982Sustainable management of water ecosystem services requires reliable information to support decision making. We evaluate the performance of the InVEST Seasonal Water Yield Model (SWYM) against water monitoring records in 224 catchments in southern Chile. We run the SWYM in three years (1998, 2007 and 2013) to account for recent land-use change and climatic variations. We computed squared Pearson correlations between SWYM monthly quickflow predictions and streamflow observations and applied a generalized mixed‐effects model to evaluate annual estimations. Results show relatively low monthly correlations with marked latitudinal and temporal variations while annual estimates show a good match between observed and modeled values, especially for values under 1000 mm/year. Better predictions were observed in regions with high rainfall and in dry years while poorer predictions were found in snow dominated and drier regions. Our results improve SWYM performance and contribute to water supply and regulation decision-making, particularly in data scarce regions.Environmental Modelling & Software13648152 Reuters ISIecosystems, forecasting, hydrogeology, land use, water management, water supply, climatic variation, land-use change, model prediction, pearson correlation, sustainable management, temporal variation, water ecosystems, water monitoring, decision making, decision support system, ecosystem service, estimation method, least squares method, performance assessment, prediction, streamflow, sustainable development, water supply, chile
Multiscale physical background to an exceptional harmful algal bloom of Dinophysis acuta in a fjord systemDíaz, Patricio A.; Peréz-Santos, Iván; Álvarez, Gonzalo; Garreaud, René; Pinilla, Elías; Díaz, Manuel; Sandoval, Alondra; Araya, Michael; Álvarez, Francisco; Rengel, José; Montero, Paulina; Pizarro, Gemita; López, Loreto; Iriarte, Luis; Igor, Gabriela; Reguera, BeatrizAgua y Extremos2021.010.1016/j.scitotenv.2021.145621Dinophysis acuta produces diarrhetic shellfish poisoning (DSP) toxins and pectenotoxins (PTX). It blooms in thermally-stratified shelf waters in late summer in temperate to cold temperate latitudes. Despite its major contribution to shellfish harvesting bans, little effort has been devoted to study its population dynamics in Chilean Patagonia. In 2017–2018, mesoscale distribution of harmful algal species (75 monitoring stations) revealed the initiation (late spring) and seasonal growth of a dense D. acuta population in the Aysén region, with maximal values at Puyuhuapi Fjord (PF). Vertical phytoplankton distribution and fine-resolution measurements of physical parameters along a 25-km transect in February 16th identified a 15-km (horizontal extension) subsurface thin layer of D. acuta from 4 to 8 m depth. This layer, disrupted at the confluence of PF with the Magdalena Sound, peaked at the top of the pycnocline (6 m, 15.9 °C, 23.4 psu) where static stability was maximal. By February 22nd, it deepened (8 m, 15.5 °C; 23.62 psu) following the excursions of the pycnocline and reached the highest density ever recorded (664 × 103 cells L−1) for this species. Dinophysis acuta was the dominant Dinophysis species in all microplankton net-tows/bottle samples; they all contained DSP toxins (OA, DTX-1) and PTX-2. Modeled flushing rates showed that Puyuhuapi, the only fjord in the area with 2 connections with the open sea, had the highest water residence time. Long term climate variability in the Southern hemisphere showed the effects of a Southern Annular Mode (SAM) in positive mode (+1.1 hPa) overwhelming a moderate La Niña. These effects included positive spring precipitation anomalies with enhanced salinity gradients and summer drought with positive anomalies in air (+1 °C) and sea surface (+2 °C) temperature. Locally, persistent thermal stratification in PF seemed to provide an optimal physical habitat for initiation and bloom development of D. acuta. Thus, in summer 2018, a favourable combination of meteorological and hydrographic processes of multiple scales created conditions that promoted the development of a widespread bloom of D. acuta with its epicentre at the head of Puyuhuapi fjord.Science of The Total Environment00489697 Reuters ISIalgae control, oceanography, plankton, plants (botany), population statistics, residence time distribution, shellfish, surface waters, diarrhetic shellfish poisoning, harmful algal blooms, long-term climate variability, mesoscale distribution, phytoplankton distributions, southern annular mode, thermally stratified, water residence time, protozoa, alga, algal bloom, climate effect, climate variation, flagellate, geographical distribution, growth rate, poisoning, population dynamics, southern hemisphere, toxin, alga, algal bloom, algal growth, article, chile, climate change, dinophysis acuta, environmental monitoring, hydrography, meteorological phenomena, microplankton, nonhuman, physical parameters, priority journal, salinity, sea surface temperature, seasonal variation, southern hemisphere, species distribution, thermoregulation, water residence time, algal bloom, dinoflagellate, estuary, human, chile, patagonia, dinophysis acuta, shellfish poisoning, chile, dinoflagellida, estuaries, harmful algal bloom, humans, shellfish poisoning
Progressive water deficits during multiyear droughts in basins with long hydrological memory in ChileAlvarez-Garreton, Camila; Boisier, Juan Pablo; Garreaud, René; Seibert, Jan; Vis, MarcAgua y Extremos2021.010.5194/hess-25-429-2021Abstract. A decade-long (2010–2020) period with precipitation deficits in central–south Chile (30–41∘ S), the so-called megadrought (MD), has led to streamflow depletions of larger amplitude than expected from precipitation anomalies, indicating an intensification in drought propagation. We analysed the catchment characteristics and runoff mechanisms modulating such intensification by using the CAMELS-CL dataset and simulations from the HBV hydrological model. We compared annual precipitation–runoff (P–R) relationships before and during the MD across 106 basins with varying snow-/rainfall regimes and identified those catchments where drought propagation was intensified. Our results show that catchments' hydrological memory – modulated by snow and groundwater – is a key control of drought propagation. Snow-dominated catchments (30–35∘ S) feature larger groundwater contribution to streamflow than pluvial basins, which we relate to the infiltration of snowmelt over the Western Andean Front. This leads to longer memory in these basins, represented by a significative correlation between autumn streamflow (when snow has already melted) and the precipitation from the preceding year. Hence, under persistent drought conditions, snow-dominated catchments accumulate the effects of precipitation deficits and progressively generate less water, compared with their historical behaviour, notably affecting central Chile, a region with limited water supply and which concentrates most of the country's population and water demands. Finally, we addressed a general question: what is worse – an extreme single-year drought or a persistent moderate drought? In snow-dominated basins, where water provision strongly depends on both the current and previous precipitation seasons, an extreme drought induces larger absolute streamflow deficits; however persistent deficits induce a more intensified propagation of the meteorological drought. Hence, the worst scenario would be an extreme meteorological drought following consecutive years of precipitation below average, as occurred in 2019. In pluvial basins of southern Chile (35–41∘ S), hydrologic memory is still an important factor, but water supply is more strongly dependant on the meteorological conditions of the current year, and therefore an extreme drought would have a higher impact on water supply than a persistent but moderate drought.Hydrology and Earth System Sciences1607-7938 Reuters ISIcatchments, groundwater, runoff, snow, stream flow, water supply, annual precipitation, catchment characteristics, hydrological modeling, limited water supplies, meteorological condition, meteorological drought, precipitation anomalies, precipitation deficits, drought, catchment, drought, groundwater-surface water interaction, hydrological modeling, meteorology, precipitation (climatology), rainfall, runoff, snowmelt, streamflow, chile
Water management or megadrought: what caused the Chilean Aculeo Lake drying?Barría, Pilar; Chadwick, Cristián; Ocampo-Melgar, Anahí; Galleguillos, Mauricio; Garreaud, Rene; Díaz-Vasconcellos, Raúl; Poblete, David; Rubio-Álvarez, Eduardo; Poblete-Caballero, DagobertoCambio de Uso de Suelo; Agua y Extremos2021.010.1007/s10113-021-01750-wThe Aculeo Lake is an important natural reservoir of Central Chile, which provides valuable ecosystem services. This lake has suffered a rapid shrinkage of the water levels from year 2010 to 2018, and since October 2018, it is completely dry. This natural disaster is concurrent with a number of severe and uninterrupted drought years, along with sustained increases in water consumption associated to land use/land cover (LULC) changes. Severe water shortages and socio-environmental impacts were triggered by these changes, emphasizing the need to understand the causes of the lake desiccation to contribute in the design of future adaptation strategies. Thereby, the Water Evaluation and Planning (WEAP) hydrological model was used as a tool to quantify the water balance in the catchment. The model was run under a combination of three land use/land cover and two different climate scenarios that sample the cases with and without megadrought and with or without changes in land use. According to the results, the main triggering factor of the lake shrinkage is the severe megadrought, with annual rainfall deficits of about 38%, which resulted in amplified reductions in river flows (44%) and aquifer recharges (24%). The results indicate that the relative impact of the climate factor is more than 10 times larger than the impact of the observed LULC changes in the lake balance, highlighting the urgent need for adaptation strategies to deal with the projected drier futures.Regional Environmental Change1436-3798, 1436-378X Reuters ISIanthropogenic, attribution, decision making, drought, land use/land cover, water budget
Assessment of GPM IMERG satellite precipitation estimation and its dependence on microphysical rain regimes over the mountains of south-central ChileRojas, Yazmina; Minder, Justin R.; Campbell, Leah S.; Massmann, Adam; Garreaud, ReneAgua y Extremos2021.010.1016/j.atmosres.2021.105454Satellite data provide crucial information for those places lacking precipitation observations from ground-based sensors, especially over oceans, mountain regions, or developing countries. This is the case over much of South America, including Chile, a country with complex topography that has limited long-term precipitation records and high-elevation data, and no operational weather radars. This study focuses on investigating the skill of the Global Precipitation Measurement (GPM) Integrated Multi-Satellite Retrieval for GPM (IMERG: version 6) quantitative precipitation estimation (QPE). IMERG is assessed against ground-based observations from two field campaigns that took place near 36°S: The Chilean Coastal Orographic Precipitation Experiment (CCOPE; winter 2015), which collected data over the coastal mountain range, and The Chilean Orographic and Mesoscale Precipitation Study (ChOMPS; winter 2016), which collected observations in a transect from the coast to the Andes. To characterize how IMERG performance depends on microphysical regime, we used data from profiling radars and rain gauge measurements to classify rainfall into regimes including “ice-initiated rain” and “warm rain”, characterized by the presence or absence of a well-defined melting layer respectively. Rain gauge data was used to evaluate performance of IMERG QPE overall and for these two regimes. IMERG depicts the general spatial pattern of observed orographic enhancement but highly underestimates the magnitude of this enhancement. At higher elevations during CCOPE, IMERG underestimated the total amount of rainfall by 50%, while during ChOMPS the underestimation was by 16%. For CCOPE, at higher elevation sites, IMERG underestimated ice-initiated rain by 30% and underestimated warm rain by 70%. For ChOMPS, the underestimation at the Andes site was 33% for ice-initiated rain and 50% for warm rain. IMERG QPE for both field campaigns showed larger underestimations for warm rain periods and at higher elevations than for ice-initiated rain periods. Documenting how IMERG performance varies with terrain and microphysical regime may help guide improvements to satellite-based QPE.Atmospheric Research0169-8095 Reuters ISIdeveloping countries, ice, landforms, meteorological radar, radar measurement, rain gages, satellites, space-based radar, topography, complex topographies, global precipitation measurements, ground based sensors, ground-based observations, orographic enhancement, orographic precipitation, quantitative precipitation estimation, satellite precipitation, rain, assessment method, cloud microphysics, estimation method, precipitation assessment, satellite data, satellite imagery, spatiotemporal analysis, chile
Tree growth decline as a response to projected climate change in the 21st century in Mediterranean mountain forests of ChileMatskovsky, V.; Venegas-González, A.; Garreaud, R.; Roig, Fidel A.; Gutiérrez, Alvaro G.; Muñoz, Ariel A; Le Quesne, C.; Klock, K.; Canales, C.Agua y Extremos2021.010.1016/j.gloplacha.2020.103406Global Climate Models project that observed climate trends are likely to be preserved and the number of extreme events will be increasing during the rest of the 21st century, which may have a detrimental impact on forest ecosystems. These impacts may include forest decline and widespread dieback of the most vulnerable biomes, such as the Mediterranean Forest of Central Chile (MFCC). Nothofagus macrocarpa and Austrocedrus chilensis are two canopy-dominant, endangered tree species in the mountains of MFCC. Here, we project tree growth of these species based on tree-ring width chronologies, a simplified version of a process-based model, and climate change projections. We used the tree ring information derived from ~400 trees from 12 sites distributed across MFCC in combination with the simplified version of process-based Vaganov-Shashkin tree-growth model (VS-Lite) to forecast changes in tree growth for the next four decades. Tree growth projections were made on the basis of monthly values of temperature and precipitation from the output of 35 climate models based on two ensembles of CO2 emission scenarios of the IPCC AR5 (RCP 8.5: higher-emission scenario, and RCP 2.6: lower-emission scenario). For the MFCC region these scenarios result in temperature rise ranging between 0.5 ◦C and 2.0 ◦C, and a precipitation decrease between 5% and 20% by the year 2065, as related to historical conditions. Our results showed that the VS-Lite model is capable of reproducing tree growth decline during the recent extreme dry period, i.e. 2010–2018, which supports its use for tree growth projections in the MFCC region. According to the modeling results, we find that tree growth in both N. macrocarpa and A. chilensis forests distributed in the MFCC region will be adversely affected by future climate changes, mainly starting from the year 2035, under both scenarios. Our work provides evidence of the degree of vulnerability of Mediterranean mountain forests in central Chile according to current climate change projections. The projected decline in tree growth indicates serious risks in the dynamics and survival of these forests relatively soon, so alerts are given about this situation which may require to counteract the deleterious effects of global change on vegetation in this region.Global and Planetary Change0921-8181 Reuters ISIclimate models, ecosystems, forestry, landforms, climate change projections, deleterious effects, endangered tree species, global climate model, mediterranean forest, mediterranean mountains, process-based modeling, tree growth modeling, climate change, biome, chronology, climate change, climate modeling, deciduous tree, dieback, extreme event, forest ecosystem, global change, global climate, growth, mediterranean environment, montane forest, tree, tree ring, twenty first century, chile, austrocedrus chilensis, nothofagus macrocarpa
Vegetation, disturbance, and climate history since the onset of ice-free conditions in the Lago Rosselot sector of Chiloé continental (44°S), northwestern PatagoniaMoreno, Patricio I.; Videla, Javiera; Kaffman, María José; Henríquez, Carla A.; Sagredo, Esteban A.; Jara-Arancio, Paola; Alloway, Brent V.Agua y Extremos2021.010.1016/j.quascirev.2021.106924We present results from Lago Negro, a small closed-basin lake adjacent to Lago Rosselot, to examine the vegetation and environmental history of an insufficiently studied sector of Chiloé Continental (41°30′-44°S) in northwestern Patagonia. Lake sediment cores from Lago Negro reveal 27 tephra deposited since ∼12.7 ka, including two prominent rhyodacite tephra marker beds erupted from Volcán Melimoyu, and a stratified basal clastic unit we attribute to meltwater discharge from an ice tongue that originated from Monte Queulat and covered Lago Rosselot during its expanded position, presumably Antarctic Cold Reversal in age. The pollen record shows closed-canopy North Patagonian rainforests since ∼12.7 ka, with variations in species composition and structure that suggest dynamic responses of the vegetation to past environmental changes. Vegetation responses to climate in the Lago Negro record were modulated, sometimes interrupted, by high magnitude and frequent disturbance regimes, most notably during maxima in explosive volcanic activity (∼9.5–7.2 ka and ∼3.6–1.6 ka) and heightened fire activity. Since Lago Negro is the southernmost palynological site so far investigated in the region and is located within a volcanically active sector, it provides a valuable perspective for assessing past vegetation responses along environmental gradients since the last glaciation. When compared with other sites throughout northwestern Patagonia, our record reveals a distinct north-to-south gradient in temperature and precipitation, with peak temperature and rainfall seasonality in the north, and a west-to-east gradient in disturbance regimes, with maximum frequency and magnitude of explosive volcanic events in the east. These gradients have modulated the response of rainforest vegetation to climate forcing at regional scale since ∼12.7 ka. We identify negligible differences in timing for the majority of key vegetation signals during the initial phase of the Lago Negro record, and propose that plant colonization and expansion along the ∼360 km long corridor through the Pacific slope of the northwestern Patagonian Andes was a rapid process during the Last Glacial Termination.Quaternary Science Reviews02773791 Reuters ISIclimate change, explosives, glacial geology, lakes, volcanoes, chiloe continental, disturbance paleoecology, glacier advance during the antarctic cold reversal, northwestern patagonium, patagonia, postglacial explosive volcanism, recession and stabilization during young dryas, vegetation and fire history, vegetation history, vegetation response, vegetation, climate forcing, disturbance, environmental change, environmental history, lacustrine deposit, sediment core, tephra, vegetation history, andes, chile, chiloe island, los lagos, patagonia
Recent Changes in the Low-Level Jet along the Subtropical West Coast of South AmericaAguirre, Catalina; Flores-Aqueveque, Valentina; Vilches, Pablo; Vásquez, Alicia; Rutllant, José A.; Garreaud, RenéZonas Costeras; Agua y Extremos2021.010.3390/atmos12040465Surface winds along the subtropical west coast of South America are characterized by the quasi-weekly occurrences of low-level jet events. These short lived but intense wind events impact the coastal ocean environment. Hence, identifying long-term trends in the coastal low-level jet (CLLJ) is essential for understanding changes in marine ecosystems. Here we use ERA5 reanalysis (1979–2019) and an objective algorithm to track anticyclones to investigate recent changes in CLLJ events off central Chile (25–43 °S). Results present evidence that the number of days with intense wind (≥10 ms−1), and the number and duration of CLLJ events have significantly changed off central Chile in recent decades. There is an increase in the number of CLLJ events in the whole study area during winter (June-July-August; JJA), while during summer (December–January–February; DJF) a decrease is observed at lower latitudes (29–34 °S), and an increase is found at the southern boundary of the Humboldt system. We suggest that changes in the central pressures and frequency of extratropical, migratory anticyclones that reach the coast of South America, which force CLLJs, have played an important role in the recent CLLJ changes observed in this region.Atmosphere2073-4433 Reuters ISIatmospheric pressure, tropics, central chile, coastal ocean environment, extratropical, long-term trend, low level jet, south america, surface winds, wind events, ecosystems, algorithm, anticyclone, climate modeling, coastal zone, jet, long-term change, surface wind, upwelling, chile
Evaluating adaptation to drought in a changing climate: experience at the local scale in the Aconcagua ValleyAldunce, Paulina; Lillo-Ortega, Gloria; Araya-Valenzuela, Dámare; Maldonado-Portilla, Pamela; Gallardo, LauraCiudades Resilientes; Agua y Extremos2021.010.1080/17565529.2021.1893150Since 2010, a severe drought has affected central Chile, resulting in losses that prompt the need to evaluate and improve adaptation responses. The evaluation process requires the engagement of multiple actors in order to collect knowledge of their experiences and to inform future design and implementation of adaptation responses. A case study was conducted in four counties of the Aconcagua Valley, Chile, to evaluate the usefulness of existing drought response measures, and to identify strengths and weaknesses, and relevant actors’ recommendations for overcoming them. We applied the Index for the Usefulness of Adaptation Practices (IUPA), a multi-criteria tool that systematically identifies the perceived usefulness of measures. The most salient strengths of the evaluated measures were: replicability, pertinence, and efficacy; representing key factors that could facilitate the implementation of drought responses in similar contexts. The most salient weaknesses were: lack of integration with other policy domains and projects, low environmental protection, diminished autonomy in decision-making, and inequity. Proposed recommendations to overcome these weaknesses have real potential for implementation because they emerged from local actors. Results present empirical evidence of the utility of participatory approaches for a context-specific evaluation of measures, contributing to enhance adaptation to climate variability and change.Climate and Development1756-5529, 1756-5537 Reuters ISIchile, climate change, drought, evaluation of adaptation, index for the usefulness of adaptation practices (iupa)
Identifying key driving mechanisms of heat waves in central ChileDemortier, Alan; Bozkurt, Deniz; Jacques-Coper, MartínZonas Costeras; Agua y Extremos2021.010.1007/s00382-021-05810-zThis study explores the main drivers of heat wave (HW) events in central Chile using state-of-the-art reanalysis data (ERA5) and observations during the extended austral summer season (November to March) for the period 1979–2018. Frequency and intensity aspects of the HW events are considered using the total number of the HW events per season and the amplitude. We first contrast ERA5 with several surface meteorological stations in central Chile to evaluate its ability to capture daily maximum temperature variability and the HW events. We then use synoptic- and large-scale fields and teleconnection patterns to address the most favorable conditions of the HW events from a climatological perspective as well as from the extreme January 2017 HW event that swept central Chile with temperature records and wildfires. ERA5 tends to capture temperature extremes and the HW events at the inland stations; on the contrary, it has difficulties in capturing the maximum temperature variability at the coastal stations, which is plausible given the complex terrain features and confined coastal climate zone (only ∼7% of all grid boxes within central Chile). The composite HW days based on ERA5 reveals a mid-level trough-ridge dipole pattern exhibiting a blocking anticyclone on the surface over a large part of southwest South America. Relatively dry and warm easterly flow appears to accompany the anomalous warming in a large part of central Chile. The temporal evolution of the HW events yields a wave-like propagation pattern and enhancement of trough-ridge pattern along the South Pacific. This meridional dipole pattern is found to be largely associated with the Pacific South American pattern. In addition, the Madden–Julian Oscillation (MJO) appears to be a key component of the HW events in central Chile. In particular, while active MJO phases 2 and 7 promote sub-seasonal patterns that favor the South Pacific dipole mode, synoptic anomalies can superimpose on them and favor the formation of a migrating anticyclone over central-southern Chile and coastal lows over central Chile. Agreeing with the climatological findings, the extreme January 2017 HW analysis suggests that an eastward migratory mid-latitude trough-ridge pattern associated with MJO phase 2 was at work. We highlight that in addition to large- and synoptic-scale features, sub-synoptic processes such as coastal lows can have an important role in shaping the HW events and can lead to amplification of temperature extremes during the HW events.Climate Dynamics0930-7575, 1432-0894 Reuters ISIatmospheric teleconnections, blocking pattern, central chile, heat waves, mjo, temperature extremes
Development and resilience of deciduous Nothofagus forests since the Last Glacial Termination and deglaciation of the central Patagonian AndesVilla-Martínez, Rodrigo; Moreno, Patricio I.Agua y Extremos2021.010.1016/j.palaeo.2021.110459Resolving the history of vegetation, fire, and glaciation on the eastern slope of the central Patagonian Andes (44°-49°S) since the Last Glacial Termination (T1) has proved difficult. This is due to the steep environmental gradients, vegetation heterogeneity, and scarcity of dated glacial deposits and geomorphic features. Unsurprisingly, published records show important heterogeneities which limit our understanding of the timing and magnitude of climate and vegetation changes, and their driving mechanisms since T1. In this paper, we describe sediment cores from small closed-basin lakes located in the deciduous Nothofagus forest zone near Coyhaique, Chile. Our results indicate that the Coyhaique glacier lobe abandoned its final Last Glacial Maximum position just before ~17.9 cal kyr BP and underwent a step-wise recession that included a halt/readvance that culminated at ~16.8 cal kyr BP, contemporaneous with the formation of an ice-dammed proglacial lake in the Coyhaique/Balmaceda sector. This glacial lake stood at its highest level between ~17.9–17.2 cal kyr BP (<726 and > 650 m.a.s.l.), lowered between ~17.2–16.2 cal kyr BP (<650 and > 570 m.a.s.l.), and disappeared thereafter. Herbs and shrubs, currently dominant in high Andean and Patagonian steppe environments, colonized the ice-free terrains distal to the glacier margins and proglacial lakes under cold and dry conditions. This was followed by a steady increase in Nothofagus between ~16.6–14.8 cal kyr BP that led to the establishment of forests starting at ~14.8 cal kyr BP. The Holocene started with a sudden increase in Nothofagus and disappearance of conifers in the context of increase fire activity between ~11.7–9.4 cal kyr BP. Closed-canopy Nothofagus forests persisted virtually unaltered from ~9.4 cal kyr BP to the present day, despite frequent explosive volcanism and millennial-scale variations in fire regimes, attesting to their extraordinary postglacial resilience which contrasts with their behavior during T1. Recent large-scale deforestation by fire, livestock grazing, and the spread of non-native invasive plant species drove the fastest and largest-magnitude shifts seen during the last ~16,500 years.Palaeogeography, Palaeoclimatology, Palaeoecology00310182 Reuters ISIdeciduous forest, deglaciation, ecosystem resilience, forest canopy, glacial lake, holocene, last glacial maximum, proglacial environment, sediment core, andes, coihaique, patagonia, coniferophyta, nothofagus
Influence of African Atmospheric Rivers on Precipitation and Snowmelt in the Near East's HighlandsBozkurt, D.; Sen, O. L.; Ezber, Y.; Guan, B.; Viale, M.; Caglar, F.Agua y Extremos2021.010.1029/2020JD033646Atmospheric rivers (ARs) traveling thousands of kilometers over arid North Africa could interact with the highlands of the Near East (NE), and thus affect the region's hydrometeorology and water resources. Here, we use a state-of-the-art AR tracking database, and reanalysis and observational datasets to investigate the climatology (1979–2017) and influences of these ARs in snowmelt season (March–April). The Red Sea and northeast Africa are found to be the major source regions of these ARs, which are typically associated with the eastern Mediterranean trough positioned over the Balkan Peninsula and a blocking anticyclone over the NE-Caspian region, triggering southwesterly air flow toward the NE's highlands. Approximately 8% of the ARs are relatively strong (integrated water vapor transport>275kg m1 s1). AR days exhibit enhanced precipitation over the crescent-shaped orography of the NE region. Mean AR days indicate wetter (up to+2mm day1) and warmer (up to+1.5°C) conditions than all-day climatology. On AR days, while snowpack tends to decrease (up to 30%) in the Zagros Mountains, it can show decreases or increases in the Taurus Mountains depending largely on elevation. A further analysis with the observations and reanalysis indicates that extreme ARs coinciding with large scale sensible heat transport can significantly increase the daily discharges. These results suggest that ARs can have notable impacts on the hydrometeorology and water resources of the region, particularly of lowland Mesopotamia, a region that is famous with great floods in the ancient narratives.Journal of Geophysical Research: Atmospheres2169-897X, 2169-8996 Reuters ISIairflow, anticyclone, atmospheric moisture, hydrometeorology, orography, precipitation assessment, snowmelt, trough, water vapor, balkans, indian ocean, mesopotamia, north africa, red sea [indian ocean], taurides, turkey, zagros
Leaf Thermal and Chemical Properties as Natural Drivers of Plant Flammability of Native and Exotic Tree Species of the Valparaíso Region, ChileGuerrero, Fabián; Hernández, Carla; Toledo, Mario; Espinoza, Lorena; Carrasco, Yulian; Arriagada, Andrés; Muñoz, Ariel; Taborga, Lautaro; Bergmann, Jan; Carmona, CamiloAgua y Extremos2021.010.3390/ijerph18137191Forest fires are one of the main environmental threats in Chile. Fires in this Mediterranean climate region frequently affect native forests and exotic plantations, including in several cases urban and rural settlements. Considering the scarcity of information regarding the fire response dynamics of tree species that are frequently affected by fires, this study aims to establish a flammability classification according to the evolution of the fire initiation risk presented by the most affected forest species in the Valparaíso region. Three exotic species, Eucalyptus globulus, Pinus radiata, and Acacia dealbata, and two native species, Cryptocarya alba and Quillaja saponaria, were studied. Flammability assays indicate that E. globulus, A. dealbata, and C. alba are extremely flammable, whereas P. radiata and Q. saponaria are flammable. Furthermore, E. globulus and A. dealbata have the highest heating values while Q. saponaria has the lowest values. The extreme flammability of E. globulus, A. dealbata, and C. alba indicates a high susceptibility to ignite. Furthermore, the high heat of combustion of E. globulus and A. dealbata can be associated with a high energy release, increasing the risk of fires spreading. In contrast, Q. saponaria has the lowest predisposition to ignite and capacity to release heat. Accordingly, this work shows that all studied tree species contain organic metabolites that are potentially flammable (sesquiterpenes, aliphatic hydrocarbons, alcohol esters, ketones, diterpenes, and triterpenes) and can be considered as drivers of flammability in vegetation. Finally, these preliminary results will aid in the construction of more resilient landscapes in the near future.International Journal of Environmental Research and Public Health1660-4601 Reuters ISIaliphatic hydrocarbon, fire behavior, fire management, forest fire, leaf, mediterranean environment, metabolite, physicochemical property, risk assessment, vegetation classification, chile, valparaiso [chile], acacia dealbata, cryptocarya alba, eucalyptus globulus, pinus radiata, quillaja saponaria, radiata, saponaria, chile, fire, forest, plant leaf, southern europe, tree, chile, fires, forests, mediterranean region, plant leaves, trees
Oceanography time series reveals annual asynchrony input between oceanic and estuarine waters in Patagonian fjordsPérez-Santos, Iván; Díaz, Patricio A.; Silva, Nelson; Garreaud, René; Montero, Paulina; Henríquez-Castillo, Carlos; Barrera, Facundo; Linford, Pamela; Amaya, Constanza; Contreras, Sergio; Aracena, Claudia; Pinilla, Elías; Altamirano, Robinson; Vallejos, Luis; Pavez, Javiera; Maulen, JuanAgua y Extremos2021.010.1016/j.scitotenv.2021.149241The postglacial Patagonian fjord system along the west coast of southern South America is one of the largest stretches of the southern hemisphere (SH) fjord belt, influenced by the SH westerly wind belt and continental freshwater input. This study reports a 3-year monthly time series (2017–2020) of physical and biogeochemical parameters obtained from the Reloncaví Marine Observatory (OMARE, Spanish acronym) at the northernmost embayment and fjord system of Patagonia. The main objective of this work was to understand the land–atmosphere–ocean interactions and to identify the mechanisms that modulate the density of phytoplankton. A key finding of this study was the seasonally varying asynchronous input of oceanic and estuarine water. Surface lower salinity and warmer estuarine water arrived in late winter to summer, contributing to water column stability, followed by subsurface higher salinity and less warmer oceanic water during fall–winter. In late winter 2019, an interannual change above the picnocline due to the record-high polarity of the Indian Ocean Dipole inhibited water column stability. The biogeochemical parameters (NO3−, NO2−, PO43−, Si(OH)4, pH, and dissolved oxygen) responded to the surface annual salinity variations, and oceanic water mass contributed greatly to the subsurface inorganic nutrient input. The water column N/P ratio indicated that no eutrophication occurred, even under intense aquaculture activity, likely because of the high ventilation dynamics of the Reloncaví Sound. Finally, a shift in phytoplankton composition, characterized by surface chlorophyll-a maxima in late winter and deepening of spring–summer blooms related to the physicochemical conditions of the water column, was observed. Our results support the ecosystem services provided by local oceanography processes in the north Patagonian fjords. Here, the anthropogenic impact caused by economic activities could be, in part, chemically reduced by the annual ventilation cycle mediated by the exchange of oceanic water masses into Patagonian fjords.Science of The Total Environment00489697 Reuters ISIbiochemical oxygen demand, dissolved oxygen, economics, ecosystems, estuaries, eutrophication, observatories, oceanography, phytoplankton, time series, atmospheric mode, biogeochemicals, column stability, estuarine waters, marine observatories, oceanic waters, patagonian fjord, southern hemisphere, times series, water columns, biogeochemistry, oxygen, picnocline, unclassified drug, water, annual variation, biogeochemistry, estuarine dynamics, estuarine environment, eutrophication, fjord, land-atmosphere interaction, land-sea interaction, nearshore dynamics, physical oceanography, southern hemisphere, time series, water column, water mass, westerly, air conditioning, aquaculture, aquatic environment, article, atmosphere, biogeochemical cycle, cell polarity, controlled study, estuary, falling, inorganic nutrient, nonhuman, oceanography, ph, physical chemistry, phytoplankton, salinity, subsurface runoff, summer, time series analysis, water column stability, winter, south america
Scientific warnings could help to reduce farmed salmon mortality due to harmful algal bloomsSoto, Doris; León-Muñoz, Jorge; Garreaud, René; Quiñones, Renato A.; Morey, FranciscoAgua y Extremos2021.010.1016/j.marpol.2021.104705The increasing occurrence of harmful algal blooms (HABs) affecting mariculture has been related to climatic factors but also to increasing eutrophication of coastal zones, to which aquaculture may also contribute. The role of climate change on HABs may be increasingly relevant but scientific efforts to separate this from other causal factors are to date inconclusive. HABs have been a permanent threat to the aquaculture industry in southern Chile, yet government and farmers may have not paid enough attention to scientific information and advice, even when risk-based predictions and warnings have been provided. Here we describe eutrophication risk assessments for water bodies hosting salmon farms and climate change risk maps for the salmon industry in Chilean Patagonia, including the increase of HABs as a main threat. Assessments and maps were delivered in 2020 both to producers and to government. We show that such risk information and mapping could have lessened recent salmon mortality due to HABs (March-April 2021) if government and farmers had followed explicit recommendations to reduce salmon farming production in water bodies with higher risk. This measure would reduce Exposure and Sensitivity under the climate change risk framework used. We provide policy recommendations, including reviewing maximum salmon production in relevant water bodies such as fjords according to eutrophication risks, while paying attention to additional stress from climate change variability and trends.Marine Policy0308597X Reuters ISIalgal bloom, aquaculture industry, aquaculture production, climate effect, coastal zone, eutrophication, governance approach, mariculture, mortality, risk assessment, salmonid culture, chile
The 21st-century fate of the Mocho-Choshuenco ice cap in southern ChileScheiter, Matthias; Schaefer, Marius; Flández, Eduardo; Bozkurt, Deniz; Greve, RalfZonas Costeras; Agua y Extremos2021.010.5194/tc-15-3637-2021Abstract. Glaciers and ice caps are thinning and retreating along the entire Andes ridge, and drivers of this mass loss vary between the different climate zones. The southern part of the Andes (Wet Andes) has the highest abundance of glaciers in number and size, and a proper understanding of ice dynamics is important to assess their evolution. In this contribution, we apply the ice-sheet model SICOPOLIS (SImulation COde for POLythermal Ice Sheets) to the Mocho-Choshuenco ice cap in the Chilean Lake District (40∘ S, 72∘ W; Wet Andes) to reproduce its current state and to project its evolution until the end of the 21st century under different global warming scenarios. First, we create a model spin-up using observed surface mass balance data on the south-eastern catchment, extrapolating them to the whole ice cap using an aspect-dependent parameterization. This spin-up is able to reproduce the most important present-day glacier features. Based on the spin-up, we then run the model 80 years into the future, forced by projected surface temperature anomalies from different global climate models under different radiative pathway scenarios to obtain estimates of the ice cap's state by the end of the 21st century. The mean projected ice volume losses are 56±16 % (RCP2.6), 81±6 % (RCP4.5), and 97±2 % (RCP8.5) with respect to the ice volume estimated by radio-echo sounding data from 2013. We estimate the uncertainty of our projections based on the spread of the results when forcing with different global climate models and on the uncertainty associated with the variation of the equilibrium line altitude with temperature change. Considering our results, we project a considerable deglaciation of the Chilean Lake District by the end of the 21st century.The Cryosphere1994-0424 Reuters ISIclimate modeling, deglaciation, equilibrium line, glacier dynamics, ice cap, ice sheet, surface temperature, twenty first century, andes, los rios [chile], mocho-choshuenco, southern volcanic zone
How well do gridded precipitation and actual evapotranspiration products represent the key water balance components in the Nile Basin?McNamara, Ian; Baez-Villanueva, Oscar M.; Zomorodian, Ali; Ayyad, Saher; Zambrano-Bigiarini, Mauricio; Zaroug, Modathir; Mersha, Azeb; Nauditt, Alexandra; Mbuliro, Milly; Wamala, Sowed; Ribbe, LarsAgua y Extremos2021.010.1016/j.ejrh.2021.100884Study region: Nile Basin, Africa. Study focus: The accurate representation of precipitation (P) and actual evapotranspiration (ETa) patterns is crucial for water resources management, yet there remains a high spatial and temporal variability among gridded products, particularly over data-scarce regions. We evaluated the performance of eleven state-of-the-art P products and seven ETa products over the Nile Basin using a four-step procedure: (i) P products were evaluated at the monthly scale through a point-to-pixel approach; (ii) streamflow was modelled using the Random Forest machine learning technique, and simulated for well-performing catchments for 2009–2018 (to correspond with ETa product availability); (iii) ETa products were evaluated at the multiannual scale using the water balance method; and (iv) the ability of the best-performing P and ETa products to represent monthly variations in terrestrial water storage (ΔTWS) was assessed through a comparison with GRACE Level-3 data. New hydrological insights for the region: CHIRPSv2 was the best-performing P product (median monthly KGE’ of 0.80) and PMLv2 and WaPORv2.1 the best-performing ETa products over the majority of the evaluated catchments. The application of the water balance using these best-performing products captures the seasonality of ΔTWS well over the White Nile Basin, but overestimates seasonality over the Blue Nile Basin. Our study demonstrates how gridded P and ETa products can be evaluated over extremely data-scarce conditions using an easily transferable methodology.Journal of Hydrology: Regional Studies22145818 Reuters ISIevapotranspiration, grace, precipitation, random forest, remote sensing, water balance
Diversifying Chile’s climate action away from industrial plantationsHoyos-Santillan, Jorge; Miranda, Alejandro; Lara, Antonio; Sepulveda-Jauregui, Armando; Zamorano-Elgueta, Carlos; Gómez-González, Susana; Vásquez-Lavín, Felipe; Garreaud, Rene D.; Rojas, MaisaCambio de Uso de Suelo; Agua y Extremos; Gobernanza e Interfaz Ciencia y Política2021.010.1016/j.envsci.2021.06.013As president of the Climate Change Conference of the Parties, Chile has advocated for developing ambitious commitments to mitigate greenhouse gas emissions to achieve carbon-neutrality by 2050. However, Chile’s motivations and ambitious push to reach carbon-neutrality are complicated by a backdrop of severe drought, climate change impacts (i.e., wildfires, tree mortality), and the use of industrial plantations as a mitigation strategy. This has become more evident as widespread and severe wildfires have impacted large areas of industrial plantations, transforming the land-use, land-use change, and forestry sector from a carbon sink to a net carbon source. Consequently, Chile must diversify its climate actions to achieve carbon-neutrality. Nature-based solutions, including wetlands-peatlands and oceans, represent alternative climate actions that can be implemented to tackle greenhouse gas emissions at a national level. Diversification, however, must guarantee Chile’s long-term carbon sequestration capacity without compromising the ecological functionality of biodiverse treeless habitats and native forest ecosystems.Environmental Science & Policy14629011 Reuters ISIcarbon, biodiversity, building, carbon footprint, carbon sequestration, carbon sink, carbon source, chile, climate, climate change, drought, electric power plant, energy yield, forest, forestry, housing, land use, note, peatland, plantation, sea, tree, wetland, wildfire
High-Frequency Variability of the Surface Ocean Properties Off Central Chile During the Upwelling SeasonAguirre, Catalina; Garreaud, René; Belmar, Lucy; Farías, Laura; Ramajo, Laura; Barrera, FacundoZonas Costeras; Agua y Extremos2021.010.3389/fmars.2021.702051The ocean off south-central Chile is subject to seasonal upwelling whose intensity is mainly controlled by the latitudinal migration of the southeast Pacific subtropical anticyclone. During austral spring and summer, the mean flow is equatorward favoring coastal upwelling, but periods of strong southerly winds are intermixed with periods of relaxed southerlies or weak northerly winds (downwelling favorable). This sub-seasonal, high-frequency variability of the coastal winds results in pronounced changes in oceanographic conditions and air-sea heat and gas exchanges, whose quantitative description has been limited by the lack of in-situ monitoring. In this study, high frequency fluctuations of meteorological, oceanographic and biogeochemical near surface variables were analyzed during two consecutive upwelling seasons (2016–17 and 2017–18) using observations from a coastal buoy located in the continental shelf off south-central Chile (36.4°S, 73°W), ∼10 km off the coast. The radiative-driven diel cycle is noticeable in meteorological variables but less pronounced for oceanographic and biogeochemical variables [ocean temperature, nitrate (NO 3 −), partial pressure of carbon dioxide ( p CO 2 sea ), pH, dissolved oxygen (DO)]. Fluorescence, as a proxy of chlorophyll- a , showed diel variations more controlled by biological processes. In the synoptic scale, 23 active upwelling events (strong southerlies, lasting between 2 and 15 days, 6 days in average) were identified, alternated with periods of relaxed southerlies of shorter duration (4.5 days in average). Upwelling events were related to the development of an atmospheric low-level coastal jet in response to an intense along-shore pressure gradient. Physical and biogeochemical surface seawater properties responded to upwelling favorable wind stress with approximately a 12-h lag. During upwelling events, SST, DO and pH decrease, while NO 3 −, p CO 2 sea , and air-sea fluxes increases. During the relaxed southerly wind periods, opposite tendencies were observed. The fluorescence response to wind variations is complex and diverse, but in many cases there was a reduction in the phytoplankton biomass during the upwelling events followed by higher values during wind relaxations. The sub-seasonal variability of the coastal ocean characterized here is important for biogeochemical and productivity studies.Frontiers in Marine Science2296-7745 Reuters ISIair-sea exchanges, biogeochemical properties, coastal buoy observations, coastal upwelling, coastal winds, eastern boundary conditions, sub-seasonal variability
Spatiotemporal Peatland Productivity and Climate Relationships Across the Western South American AltiplanoAnderson, Talia G.; Christie, Duncan A.; Chávez, Roberto O.; Olea, Matias; Anchukaitis, Kevin J.Agua y Extremos2021.010.1029/2020JG005994The South American Altiplano is one of the largest semiarid high-altitude plateaus in the world. Within the Altiplano, peatlands known as “bofedales” are important components of regional hydrology and provide key water resources and ecosystem services to Andean communities. Warming temperatures, changes in hydroclimate, and shifting atmospheric circulation patterns all affect peatland dynamics and hydrology. It is therefore urgent to better understand the relationships between climate variability and the spatiotemporal variations in peatland productivity across the Altiplano. Here, we explore climate influences on peatland vegetation using 31 years of Landsat data. We focus specifically on the bofedal network in the western Altiplano, the driest sector of the plateau, and use the satellite-derived Normalized Difference Vegetation Index (NDVI) as an indicator of productivity. We develop temporally and spatially continuous NDVI products at multiple scales in order to evaluate relationships with climate variables over the past three decades. We demonstrate that cumulative precipitation and snow persistence over the prior 2 years are strongly associated with growing season productivity. A step change in peatland productivity between 2013–2015 drives an increasing trend in NDVI and is likely a response to consecutive years of anomalously high snow accumulation and rainfall. Early summer minimum temperatures emerge as a secondary influence on productivity. Understanding large-scale productivity dynamics and characterizing the response of bofedales to climate variability over the last three decades provides a baseline to monitor the responses of Andean peatlands to climate change.Journal of Geophysical Research: Biogeosciences2169-8953, 2169-8961 Reuters ISIatmospheric circulation, climate change, growing season, ndvi, peatland, precipitation (chemistry), precipitation (climatology), rainfall, snow accumulation, spatiotemporal analysis, altiplano, indicator indicator, varanidae
Chemical Signals in Tree Rings from Northern Patagonia as Indicators of Calbuco Volcano Eruptions since the 16th CenturyBertin, Lizette J.; Christie, Duncan A.; Sheppard, Paul R.; Muñoz, Ariel A.; Lara, Antonio; Alvarez, ClaudioCambio de Uso de Suelo; Agua y Extremos2021.010.3390/f12101305The Calbuco volcano ranks third in the specific risk classification of volcanoes in Chile and has a detailed eruption record since 1853. During 2015, Calbuco had a sub-Plinian eruption with negative impacts in Chile and Argentina, highlighting the need to determine the long-term history of its activity at a high-resolution time scale to obtain a better understanding of its eruptive frequency. We developed a continuous eruptive record of Calbuco for the 1514–2016 period by dendrochemical analysis of Fitzroya cupressoides tree rings at a biennium resolution using inductively coupled plasma–mass spectrometry. After comparing the chemical record of 20 elements contained in tree rings with historical eruptions, one group exhibited positive anomalies during (Pb/Sn) and immediately after (Mo/P/Zn/Cu) eruptions, with a Volcanic Explosivity Index (VEI) ≥ 3, and so were classified as chemical tracers of past eruptions (TPE). The tree-ring width chronology also exhibited significant decreases in tree growth associated with eruptions of VEI ≥ 3. According to these records, we identified 11 new eruptive events of Calbuco, extending its eruptive chronology back to the 16th century and determining a mean eruptive frequency of ~23 years. Our results show the potential to use dendrochemical analysis to infer past volcanic eruptions in Northern Patagonia. This information provides a long-term perspective for assessing eruptive history in Northern Patagonia, with implications for territorial planning.Forests1999-4907 Reuters ISIforestry, indicators (chemical), inductively coupled plasma, mass spectrometry, chemical signals, fitzroya cupressoides, inductively coupled plasma-mass spectrometry, northern patagonia, risk classification, sub-plinian eruption, tree rings, volcanic eruptions, volcanic explosivity indices, volcano eruptions, volcanoes
Trace elements in Antarctic penguins and the potential role of guano as source of recycled metals in the Southern OceanSparaventi, Erica; Rodríguez-Romero, Araceli; Barbosa, Andrés; Ramajo, Laura; Tovar-Sánchez, AntonioZonas Costeras; Agua y Extremos2021.010.1016/j.chemosphere.2021.131423Penguins dominate the Antarctic avifauna. As key animals in the Antarctic ecosystem, they are monitored to evaluate the ecological status of this pristine and remote region and specifically, they have been used as effective bioindicators suitable for long-term monitoring of metals in the Antarctic environment. However, studies about the role of this emblematic organism could play in the recycling of trace metals (TMs) in the Antarctic ecosystem are very limited. In this study we evaluate, using the peer review research articles already published and our own findings, the distribution of metals (i.e., Ca, Fe, Al, Na, Zn, Mg, Cu, K, Cd, Mn, Sr, Cr, Ni, Pb, Hg, V, Ba, Co, La, Ag, Rb, Hf, Sc, Au and Cs) and metalloids (As and Sb), measured in different biotic matrices, with emphasis on guano, of the Chinstrap (Pygoscelis antarcticus), Adélie (Pygoscelis adeliae) and Gentoo (Pygoscelis papua) penguins. Regarding bioactive metals, the high concentrations (μg g−1 dry weight) of Cu (2.0 ± 1.4) x 102, Fe (4.1 ± 2.9) x 102, Mn (30 ± 34) and Zn (210 ± 90) reported in the guano from all the penguin species studied including our data, are of the same order of magnitude as those reported for whale feces (μg g−1 dry weight): Cu (2.9 ± 2.4) x 102, Fe (1.5 ± 1.4) x 102, Mn (28 ± 17) and Zn (6.2 ± 4.3) x 102, and one order of magnitude higher than the metal contents in krill (μg g−1 dry weight) of Cu (10.2 ± 5.5), Fe (24 ± 29) and Zn (13.5 ± 1.7). This suggest that penguin's excretion products could be an important source of these essential elements in the surface water, with an estimated annual release on a breeding season for Cu, Fe, Mn, Zn respectively of 28, 56, 4 and 29 tons, for the Chinstrap, Adélie and Gentoo penguins. The results provide evidence on the potential influence of penguins recycling TMs in the surface layer of the water column.Chemosphere00456535 Reuters ISIecosystems, recycling, surface waters, trace elements, antarctica, dropping, dry weight, ecological status, metal concentrations, orders of magnitude, remote regions, southern ocean, trace metal, traces elements, metals, avifauna, bioindicator, breeding season, concentration (composition), excretion, feces, guano, metalloid, recycling, seabird, trace element, whale, southern ocean, pygoscelis antarcticus, spheniscidae
The last glacial termination in northwestern Patagonia viewed from the Lago Fonk (∼40°S) recordHenríquez, Carla A.; Moreno, Patricio I.; Dunbar, Robert B.; Mucciarone, David A.Agua y Extremos2021.010.1016/j.quascirev.2021.107197The anatomy of the Last Glacial Termination (T1) in the southern mid-latitudes, and its relationship with changes in the Southern Westerly Winds (SWW), offers empirical constraints for understanding the mechanisms involved in the transition from the Last Glacial Maximum into the current interglacial. Northwestern Patagonia (40°-44°S) is a sensitive region for monitoring past changes in the SWW, the Patagonian Ice Sheet, terrestrial ecosystems, and fire regimes through T1. Here we present results from Lago Fonk (∼40°S) to examine the structure of T1 based on the palynological, macroscopic charcoal, elemental, and isotopic composition of organic lake sediments. We observe an instantaneous establishment of Nothofagus-dominated forests at the onset of T1, followed by a diversification and densification trend that culminated with the establishment of thermophilous, Myrtaceae-dominated North Patagonian rainforests between ∼15.6–14.7 cal ka BP. The expansion of the conifer Podocarpus nubigena marks a shift to cool-temperate and hyperhumid conditions, coeval with high lake levels and enhanced algal productivity between ∼14.7–11.9 cal ka BP. Stand-replacing fires, driven by enhanced seasonality or high-frequency rainfall variability, started at ∼12.4 cal ka BP and catalyzed the rapid spread of Weinmannia trichosperma. Subsequent warming and a decline in precipitation at ∼11.4 cal ka BP led to intense fire activity, lake-level lowering, and establishment of the Valdivian rainforest trees Eucryphia/Caldcluvia. Our results suggest a coherent linkage between changes documented in the amphi south Pacific region and Antarctic ice cores during T1. This implies a zonal and hemispheric response to changes in the position/intensity of the SWW that emphasizes their central role as a key driver of the hemispheric and global climate evolution through T1.Quaternary Science Reviews02773791 Reuters ISIfires, forestry, glacial geology, lakes, 'current, lake levels, lake sediment cores, last glacial maximum, last glacial terminations, midlatitudes, multi proxies, multi-proxy index, patagonia, southern westerly winds, charcoal, coniferophyta, eucryphia, myrtaceae, nothofagus, podocarpus nubigenus, weinmannia trichosperma
RF-MEP: A novel Random Forest method for merging gridded precipitation products and ground-based measurementsBaez-Villanueva, Oscar M.; Zambrano-Bigiarini, Mauricio; Beck, Hylke E.; McNamara, Ian; Ribbe, Lars; Nauditt, Alexandra; Birkel, Christian; Verbist, Koen; Giraldo-Osorio, Juan Diego; Xuan Thinh, NguyenAgua y Extremos2020.010.1016/j.rse.2019.111606The accurate representation of spatio-temporal patterns of precipitation is an essential input for numerous environmental applications. However, the estimation of precipitation patterns derived solely from rain gauges is subject to large uncertainties. We present the Random Forest based MErging Procedure (RF-MEP), which combines information from ground-based measurements, state-of-the-art precipitation products, and topography-related features to improve the representation of the spatio-temporal distribution of precipitation, especially in data-scarce regions. RF-MEP is applied over Chile for 2000—2016, using daily measurements from 258 rain gauges for model training and 111 stations for validation. Two merged datasets were computed: RF-MEP3P (based on PERSIANN-CDR, ERA-Interim, and CHIRPSv2) and RF-MEP5P (which additionally includes CMORPHv1 and TRMM 3B42v7). The performances of the two merged products and those used in their computation were compared against MSWEPv2.2, which is a state-of-the-art global merged product. A validation using ground-based measurements was applied at different temporal scales using both continuous and categorical indices of performance. RF-MEP3P and RF-MEP5P outperformed all the precipitation datasets used in their computation, the products derived using other merging techniques, and generally outperformed MSWEPv2.2. The merged P products showed improvements in the linear correlation, bias, and variability of precipitation at different temporal scales, as well as in the probability of detection, the false alarm ratio, the frequency bias, and the critical success index for different precipitation intensities. RF-MEP performed well even when the training dataset was reduced to 10% of the available rain gauges. Our results suggest that RF-MEP could be successfully applied to any other region and to correct other climatological variables, assuming that ground-based data are available. An R package to implement RF-MEP is freely available online at Sensing of Environment00344257 Reuters ISIdecision trees, merging, precipitation (chemical), rain gages, topography, bias correction, environmental applications, ground based measurement, precipitation products, probability of detection, random forests, rf-mep, spatiotemporal distributions, rain, algorithm, correction, data set, ground-based measurement, measurement method, model validation, numerical method, precipitation (climatology), raingauge, topography, trmm, uncertainty analysis, chile
Recent changes in the precipitation-driving processes over the southern tropical Andes/western AmazonSegura, Hans; Espinoza, Jhan Carlo; Junquas, Clementine; Lebel, Thierry; Vuille, Mathias; Garreaud, ReneAgua y Extremos2020.010.1007/s00382-020-05132-6Analyzing December–February (DJF) precipitation in the southern tropical Andes—STA (12∘S–20∘S; > 3000 m.a.s.l) allows revisiting regional atmospheric circulation features accounting for its interannual variability over the past 35 years (1982–2018). In a region where in-situ rainfall stations are sparse, the CHIRPS precipitation product is used to identify the first mode of interannual DJF precipitation variability (PC1-Andes). A network of 98 rain-gauge stations further allows verifying that PC1-Andes properly represents the spatio-temporal rainfall distribution over the region; in particular a significant increase in DJF precipitation over the period of study is evident in both in-situ data and PC1-Andes. Using the ERA-Interim data set, we found that aside from the well-known relationship between precipitation and upper-level easterlies over the STA, PC1-Andes is also associated with upward motion over the western Amazon (WA), a link that has not been reported before. The ascent over the WA is a component of the meridional circulation between the tropical North Atlantic and western tropical South America—WTSA (80∘W–60∘W; 35∘S–10∘N). Indeed, the precipitation increase over the last 2 decades is concomitant with the strengthening of this meridional circulation. An intensified upward motion over the WA has moistened the mid-troposphere over WTSA, and as a consequence, a decreased atmospheric stability between the mid- and the upper troposphere is observed over this region, including the STA. We further show that, over the last 15 years or so, the year-to-year variability of STA precipitation (periodicity < 8 years) has been significantly associated with upward motion over the WA, while upper-level easterlies are no longer significantly correlated with precipitation. These observations suggests that the STA have experienced a transition from a dry to a wet state in association with a change in the dominant mode of atmospheric circulation. In the former dominant state, zonal advection of momentum and moisture from the central Amazon, associated with upper-level easterlies, is necessary to develop convection over the STA. Since the beginning of the 21st century, DJF precipitation over the STA seems to respond directly and primarily to upward motion over the WA. Beyond improving our understanding of the factors influencing STA precipitation nowadays, these results point to the need of exploring their possible implications for the long-term evolution of precipitation in a context of global warming.Climate Dynamics0930-7575, 1432-0894 Reuters ISIannual variation, atmospheric circulation, atmospheric convection, precipitation (climatology), rainfall, troposphere, altiplano, amazonia, andes
The deglaciation of the Americas during the Last Glacial TerminationPalacios, David; Stokes, Chris R.; Phillips, Fred M.; Clague, John J.; Alcalá-Reygosa, Jesus; Andrés, Nuria; Angel, Isandra; Blard, Pierre-Henri; Briner, Jason P.; Hall, Brenda L.; Dahms, Dennis; Hein, Andrew S.; Jomelli, Vincent; Mark, Bryan G.; Martini, Mateo A.; Moreno, Patricio; Riedel, Jon; Sagredo, Esteban; Stansell, Nathan D.; Vázquez-Selem, Lorenzo; Vuille, Mathias; Ward, Dylan J.Agua y Extremos2020.010.1016/j.earscirev.2020.103113This paper reviews current understanding of deglaciation in North, Central and South America from the Last Glacial Maximum to the beginning of the Holocene. Together with paleoclimatic and paleoceanographic data, we compare and contrast the pace of deglaciation and the response of glaciers to major climate events. During the Global Last Glacial Maximum (GLGM, 26.5-19 ka), average temperatures decreased 4° to 8°C in the Americas, but precipitation varied strongly throughout this large region. Many glaciers in North and Central America achieved their maximum extent during the GLGM, whereas others advanced even farther during the subsequent Heinrich Stadial 1 (HS-1). Glaciers in the Andes also expanded during the GLGM, but that advance was not the largest, except on Tierra del Fuego. HS-1 (17.5-14.6 ka) was a time of general glacier thickening and advance throughout most of North and Central America, and in the tropical Andes; however, glaciers in the temperate and subpolar Andes thinned and retreated during this period. During the Bølling-Allerød interstadial (B-A, 14.6-12.9 ka), glaciers retreated throughout North and Central America and, in some cases, completely disappeared. Many glaciers advanced during the Antarctic Cold Reversal (ACR, 14.6-12.9 ka) in the tropical Andes and Patagonia. There were small advances of glaciers in North America, Central America and in northern South America (Venezuela) during the Younger Dryas (12.9-11.7 ka), but glaciers in central and southern South America retreated during this period, except on the Altiplano where advances were driven by an increase in precipitation. Taken together, we suggest that there was a climate compensation effect, or ‘seesaw’, between the hemispheres, which affected not only marine currents and atmospheric circulation, but also the behavior of glaciers. This seesaw is consistent with the opposing behavior of many glaciers in the Northern and Southern Hemispheres.Earth-Science Reviews0012-8252 Reuters ISIchronology, deglaciation, glacier, last glacial maximum, paleoceanography, paleoclimate, paleotemperature, precipitation (climatology), central america, north america, south america
Water Crisis in Petorca Basin, Chile: The Combined Effects of a Mega-Drought and Water ManagementMuñoz A.; Klock-Barría, Karin; Alvarez-Garreton, Camila; Aguilera-Betti, Isabella; González-Reyes, Álvaro; Lastra, José A.; Chávez, Roberto O.; Barría, Pilar; Christie, Duncan; Rojas-Badilla, Moises; Quesne, Carlos LeAgua y Extremos2020.010.3390/w12030648Since 2010, Chile has experienced one of the most severe droughts over the last century, the so-called mega-drought (MD). The MD conditions, combined with intensive agricultural activities and the current water management system, have led to water scarcity problems in Mediterranean and Semi-arid regions of Chile. An emblematic case is the Petorca basin, where a water crisis is undergone. To characterize this crisis, we analyzed water provision by using tree-ring records, remote sensing, instrumental data, and allocated water rights within the basin. Results indicate that the MD is the most severe dry period over the last 700-years of streamflow reconstruction. During the MD, streamflow and water bodies of the upper parts of the basin have been less affected than mid and low areas of this valley, where consumptive withdrawals reach up to 18% of the mean annual precipitation. This extracted volume is similar to the MD mean annual precipitation deficits. The impacts of the current drought, along with the drier climate projections for Central Chile, emphasize the urgency for faster policy changes related to water provision. Climate change adaptation plans and policies should enhance the current monitoring network and the public control of water use to secure the water access for inhabitants and productive activities.Water2073-4441 Reuters ISIagricultural robots, drought, forestry, remote sensing, stream flow, trees (mathematics), water management, agricultural activities, climate change adaptation, climate projection, current monitoring, instrumental data, mean annual precipitation, water management systems, water scarcity, climate change, drought, reconstruction, streamflow, water management, water use, chile
Validation of a 9-km WRF dynamical downscaling of temperature and precipitation for the period 1980–2005 over Central South ChileFernández, Alfonso; Schumacher, Vanúcia; Ciocca, Isabella; Rifo, Andreaw; Muñoz, Ariel A.; Justino, FlavioAgua y Extremos2020.010.1007/s00704-020-03416-9In this paper, we evaluated a dynamical downscaling produced for Central South Chile (32°S–38°S) relative to climatic conditions between 1980 and 2005. Assessing the skill of dynamical downscaling relative to the present climate is key to determine the degree of confidence on regional climatic projections. We used the Weather Research and Forecasting model to simulate that period at ~ 9 km grid-cell size, forced by the bias-corrected Community Earth System Model. Results indicated that the dynamical downscaling adequately reproduced spatio-temporal features of the climate within the region. Temperature showed a positive bias at the annual scale while the opposite occurred for precipitation. The bias varied when the comparison was performed relative to a gridded product or instrumental records from weather stations. At the monthly scale, the model failed to capture long-term trends relative to the gridded dataset while reproducing spatial patterns, especially for temperature. We found a generally statistically significant spatial clustering of the monthly mean bias that can support implementation and application of dynamical downscaling and bias-correction methods that account for the distinct climatic features of the study area. In particular, the strip 34°S–35°S presented features that are coincident with previous findings suggesting this latitude to be a boundary between different climate regimes north and south. According to our results, we assert that this dynamical downscaling is comparable with other available databases and thus can be utilized in future studies as an additional and independent source of analysis, contributing to a balanced appraisal of climate scenarios for policymaking within the region.Theoretical and Applied Climatology0177-798X, 1434-4483 Reuters ISIair temperature, climate conditions, climate prediction, computer simulation, downscaling, precipitation assessment, regional climate, weather forecasting, chile
A Network for Advancing Dendrochronology, Dendrochemistry and Dendrohydrology in South AmericaAguilera-Betti, Isabella; Lucas, Christine; Ferrero, María Eugenia; Muñoz, Ariel A.Agua y Extremos2020.010.3959/TRR2019-12Tree-ring research (TRR) in South America (SA) continues to make important contributions in multiple sub-disciplines, including dendrochemistry and dendrohydrology. 1 2 communicate recent advances in TRR within a network of laboratories in Argentina, Brazil, Chile, Peru, and Uruguay. Novel methodologies and results in dendrochemistry and wood anatomy were also presented by collaborating researchers from German institutions. The report describes some of the research within the subdisciplines of tree-ring science, including dendrochemistry, anatomy and dendrohydrology, and their application to understanding spatio-temporal variability in heavy metal contamination, climate, hydrology, fire regimes and other critical components of South American forest and woodland ecosystems. The meeting demonstrated a broadening and diversification in the research and applications of TRR in SA, whereby collaboration across research centers has been critical for the advances made in broad-scale comparative studies as well as multi-proxy approaches and the study of global and hemisphere-scale climate phenomena.Tree-Ring Research1536-1098 Reuters ISIchemical analysis, climate, pollution, stable isotopes, trace elements, tree rings, wood anatomy
Two Centuries of Hydroclimatic Variability Reconstructed From Tree‐Ring Records Over the Amazonian Andes of PeruHumanes‐Fuente, V.; Ferrero, M. E.; Muñoz, A. A.; González‐Reyes, Á.; Requena‐Rojas, E. J.; Barichivich, J.; Inga, J. G.; Layme‐Huaman, E. T.Agua y Extremos2020.010.1029/2020JD032565Almost half of the tributaries of the Amazon River originate in the tropical Andes and support large populations in mountain regions and downstream areas. However, it is difficult to assess hydroclimatic conditions or to evaluate future scenarios due to the scarcity of long, high‐quality instrumental records. Data from the Global Precipitation Climatology Project (GPCP) provide a complete record since 1979 and offer a good representation of rainfall over the tropical Andes. Longer records are needed to improve our understanding of rainfall variability and summer monsoon behavior at various scales. We developed the first annually resolved precipitation reconstruction for the tropical Andes in Peru, based on tree‐ring chronologies of Cedrela and Juglans species. The annual (November–October) reconstruction extends the short instrumental records back to 1817, explaining 68% of the total variance of precipitation over the 1979–2007 calibration period. The reconstruction reveals the well‐documented influence of El Niño‐Southern Oscillation (ENSO) on Amazon Rainfall at interannual scales (~19% of total variance) and significant multidecadal variability with alternating periods of about 40 years (~13% of rainfall variability) related to the Atlantic Multidecadal Oscillation (AMO). Both oscillatory modes can explain dry and humid periods observed within the reconstruction and are likely associated with the negative trends of rainfall in the short instrumental records and the increased drought recurrence in recent decades. Our results show that montane tropical tree rings can be used to reconstruct precipitation with exceptionally high fidelity, characterize the interannual to multidecadal variability, and identify remote forcings in the hydroclimate over the Andean Amazon Basin of Peru.Journal of Geophysical Research: Atmospheres2169-897X, 2169-8996 Reuters ISIclimate variation, decadal variation, el nino-southern oscillation, humid environment, paleoclimate, rainfall, reconstruction, tree ring, amazonia, andes, peru, cedrela, juglans
Transforming knowledge systems for life on Earth: Visions of future systems and how to get thereFazey, Ioan; Schäpke, Niko; Caniglia, Guido; Hodgson, Anthony; Kendrick, Ian; Lyon, Christopher; Page, Glenn; Patterson, James; Riedy, Chris; Strasser, Tim; Verveen, Stephan; Adams, David; Goldstein, Bruce; Klaes, Matthias; Leicester, Graham; Linyard, Alison; McCurdy, Adrienne; Ryan, Paul; Sharpe, Bill; Silvestri, Giorgia; Abdurrahim, Ali Yansyah; Abson, David; Adetunji, Olufemi Samson; Aldunce, Paulina; Alvarez-Pereira, Carlos; Amparo, Jennifer Marie; Amundsen, Helene; Anderson, Lakin; Andersson, Lotta; Asquith, Michael; Augenstein, Karoline; Barrie, Jack; Bent, David; Bentz, Julia; Bergsten, Arvid; Berzonsky, Carol; Bina, Olivia; Blackstock, Kirsty; Boehnert, Joanna; Bradbury, Hilary; Brand, Christine; Böhme (born Sangmeister), Jessica; Bøjer, Marianne Mille; Carmen, Esther; Charli-Joseph, Lakshmi; Choudhury, Sarah; Chunhachoti-ananta, Supot; Cockburn, Jessica; Colvin, John; Connon, Irena L.C.; Cornforth, Rosalind; Cox, Robin S.; Cradock-Henry, Nicholas; Cramer, Laura; Cremaschi, Almendra; Dannevig, Halvor; Day, Catherine T.; de Lima Hutchison, Cathel; de Vrieze, Anke; Desai, Vikas; Dolley, Jonathan; Duckett, Dominic; Durrant, Rachael Amy; Egermann, Markus; Elsner (Adams), Emily; Fremantle, Chris; Fullwood-Thomas, Jessica; Galafassi, Diego; Gobby, Jen; Golland, Ami; González-Padrón, Shiara Kirana; Gram-Hanssen, Irmelin; Grandin, Jakob; Grenni, Sara; Lauren Gunnell, Jade; Gusmao, Felipe; Hamann, Maike; Harding, Brian; Harper, Gavin; Hesselgren, Mia; Hestad, Dina; Heykoop, Cheryl Anne; Holmén, Johan; Holstead, Kirsty; Hoolohan, Claire; Horcea-Milcu, Andra-Ioana; Horlings, Lummina Geertruida; Howden, Stuart Mark; Howell, Rachel Angharad; Huque, Sarah Insia; Inturias Canedo, Mirna Liz; Iro, Chidinma Yvonne; Ives, Christopher D.; John, Beatrice; Joshi, Rajiv; Juarez-Bourke, Sadhbh; Juma, Dauglas Wafula; Karlsen, Bea Cecilie; Kliem, Lea; Kläy, Andreas; Kuenkel, Petra; Kunze, Iris; Lam, David Patrick Michael; Lang, Daniel J.; Larkin, Alice; Light, Ann; Luederitz, Christopher; Luthe, Tobias; Maguire, Cathy; Mahecha-Groot, Ana-Maria; Malcolm, Jackie; Marshall, Fiona; Maru, Yiheyis; McLachlan, Carly; Mmbando, Peter; Mohapatra, Subhakanta; Moore, Michele-Lee; Moriggi, Angela; Morley-Fletcher, Mark; Moser, Susanne; Mueller, Konstanze Marion; Mukute, Mutizwa; Mühlemeier, Susan; Naess, Lars Otto; Nieto-Romero, Marta; Novo, Paula; O’Brien, Karen; O'Connell, Deborah Anne; O'Donnell, Kathleen; Olsson, Per; Pearson, Kelli Rose; Pereira, Laura; Petridis, Panos; Peukert, Daniela; Phear, Nicky; Pisters, Siri Renée; Polsky, Matt; Pound, Diana; Preiser, Rika; Rahman, Md. Sajidur; Reed, Mark S.; Revell, Philip; Rodriguez, Iokiñe; Rogers, Briony Cathryn; Rohr, Jascha; Nordbø Rosenberg, Milda; Ross, Helen; Russell, Shona; Ryan, Melanie; Saha, Probal; Schleicher, Katharina; Schneider, Flurina; Scoville-Simonds, Morgan; Searle, Beverley; Sebhatu, Samuel Petros; Sesana, Elena; Silverman, Howard; Singh, Chandni; Sterling, Eleanor; Stewart, Sarah-Jane; Tàbara, J. David; Taylor, Douglas; Thornton, Philip; Tribaldos, Theresa Margarete; Tschakert, Petra; Uribe-Calvo, Natalia; Waddell, Steve; Waddock, Sandra; van der Merwe, Liza; van Mierlo, Barbara; van Zwanenberg, Patrick; Velarde, Sandra Judith; Washbourne, Carla-Leanne; Waylen, Kerry; Weiser, Annika; Wight, Ian; Williams, Stephen; Woods, Mel; Wolstenholme, Ruth; Wright, Ness; Wunder, Stefanie; Wyllie, Alastair; Young, Hannah R.Agua y Extremos2020.010.1016/j.erss.2020.101724Formalised knowledge systems, including universities and research institutes, are important for contemporary societies. They are, however, also arguably failing humanity when their impact is measured against the level of progress being made in stimulating the societal changes needed to address challenges like climate change. In this research we used a novel futures-oriented and participatory approach that asked what future envisioned knowledge systems might need to look like and how we might get there. Findings suggest that envisioned future systems will need to be much more collaborative, open, diverse, egalitarian, and able to work with values and systemic issues. They will also need to go beyond producing knowledge about our world to generating wisdom about how to act within it. To get to envisioned systems we will need to rapidly scale methodological innovations, connect innovators, and creatively accelerate learning about working with intractable challenges. We will also need to create new funding schemes, a global knowledge commons, and challenge deeply held assumptions. To genuinely be a creative force in supporting longevity of human and non-human life on our planet, the shift in knowledge systems will probably need to be at the scale of the enlightenment and speed of the scientific and technological revolution accompanying the second World War. This will require bold and strategic action from governments, scientists, civic society and sustained transformational intent.Energy Research & Social Science22146296 Reuters ISIclimate and energy research, epistemology, knowledge, social-technical transitions, sustainability science, transformation
Six hundred years of South American tree rings reveal an increase in severe hydroclimatic events since mid-20th centuryMorales, Mariano S.; Cook, Edward R.; Barichivich, Jonathan; Christie, Duncan A.; Villalba, Ricardo; LeQuesne, Carlos; Srur, Ana M.; Ferrero, M. Eugenia; González-Reyes, Álvaro; Couvreux, Fleur; Matskovsky, Vladimir; Aravena, Juan C.; Lara, Antonio; Mundo, Ignacio A.; Rojas, Facundo; Prieto, María R.; Smerdon, Jason E.; Bianchi, Lucas O.; Masiokas, Mariano H.; Urrutia-Jalabert, Rocio; Rodriguez-Catón, Milagros; Muñoz, Ariel A.; Rojas-Badilla, Moises; Alvarez, Claudio; Lopez, Lidio; Luckman, Brian H.; Lister, David; Harris, Ian; Jones, Philip D.; Williams, A. Park; Velazquez, Gonzalo; Aliste, Diego; Aguilera-Betti, Isabella; Marcotti, Eugenia; Flores, Felipe; Muñoz, Tomás; Cuq, Emilio; Boninsegna, José A.Agua y Extremos2020.010.1073/pnas.2002411117South American (SA) societies are highly vulnerable to droughts and pluvials, but lack of long-term climate observations severely limits our understanding of the global processes driving climatic variability in the region. The number and quality of SA climate-sensitive tree ring chronologies have significantly increased in recent decades, now providing a robust network of 286 records for characterizing hydroclimate variability since 1400 CE. We combine this network with a self-calibrated Palmer Drought Severity Index (scPDSI) dataset to derive the South American Drought Atlas (SADA) over the continent south of 12°S. The gridded annual reconstruction of austral summer scPDSI is the most spatially complete estimate of SA hydroclimate to date, and well matches past historical dry/wet events. Relating the SADA to the Australia–New Zealand Drought Atlas, sea surface temperatures and atmospheric pressure fields, we determine that the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) are strongly associated with spatially extended droughts and pluvials over the SADA domain during the past several centuries. SADA also exhibits more extended severe droughts and extreme pluvials since the mid-20th century. Extensive droughts are consistent with the observed 20th-century trend toward positive SAM anomalies concomitant with the weakening of midlatitude Westerlies, while low-level moisture transport intensified by global warming has favored extreme rainfall across the subtropics. The SADA thus provides a long-term context for observed hydroclimatic changes and for 21st-century Intergovernmental Panel on Climate Change (IPCC) projections that suggest SA will experience more frequent/severe droughts and rainfall events as a consequence of increasing greenhouse gas emissions.Proceedings of the National Academy of Sciences0027-8424, 1091-6490 Reuters ISIrain, atmospheric pressure, carbon footprint, controlled study, drought, environmental impact, experience, greenhouse effect, hydroclimate, moisture, nonhuman, priority journal, review, sea surface temperature, seasonal variation, soil moisture, south america, spatiotemporal analysis, tree, tree ring, climate, geographic mapping, greenhouse effect, growth, development and aging, statistical model, tree, climate, droughts, geographic mapping, global warming, models, statistical, rain, south america, trees
Tree-growth at the rear edge of a Nothofagus pumilio Andean forest from Northern Patagonia show different patterns and a decline in the common signal during the last centurySerrano-León, Hernán; Christie, Duncan A.Agua y Extremos2020.010.1016/j.foreco.2020.118426Nothofagus pumilio is the dominant tree species at high elevations in the southern Andes between 35° and 55° S. Despite the number of tree-growth studies on this tree species, there is scarce information about the growth patterns and its relation with climatic variability at its lower elevation margin of distribution in the windward side of the Andes. In this study we focus on the altitudinal rear edge of a N. pumilio forest growing on the Pacific side of the northern Patagonian Andes to determine the main temporal patterns of tree radial growth, identify its relations with regional and large-scale climate and to assess the temporal variation of common signal in tree growth at centennial time-scales. A Principal Component Analysis (PCA) between trees for their common period 1850–2010 indicates the existence of more than one pattern of tree growth within this lower altitudinal margin, which exhibit contrasting relations with climate. The tree ring chronology and the PC1 amplitude of tree growth shows negative correlation with maximum temperature during spring-summer while the PC2 shows the contrary. Maps and correlation functions indicate that the PC1 and PC2 patterns of N. pumilio growth are significantly related with high latitude climate variability induced by the Antarctic Oscillation (AAO) during spring-summer in an opposite manner, with the PC1 (PC2) negatively (positively) correlated with the poleward displacement of the storm tracks driven by the mid- and high-latitude dipole pressure in the Southern Hemisphere. The running PCA between the standardized tree ring-width series shows a decreasing trend in the percentage of variance explained by the first mode of tree growth, indicating a centennial scale loss in the common signal of growth within the population, especially since mid-20th century when the behavior of the AAO was unprecedented within the context of the last millennium. Given that the future climatic scenario for northern Patagonia as predicted by models would led to more arid conditions forced by the positive trend of the AAO, we expect that the main pattern of N. pumilio growth at the rear edge of Choshuenco volcano will be negatively affected. Despite the present knowledge about N. pumilio radial growth in treeline environments, specific research is needed to gain insights about the complexity of the climate-growth relationship at its low elevation margin, in order to evaluate anomalies in tree growth patterns in the habitat where N. pumilio grows and competes with other low elevation species more tolerant to warmer conditions.Forest Ecology and Management03781127 Reuters ISIpopulation statistics, springs (components), antarctic oscillation, climate variability, climatic variability, correlation function, maximum temperature, negative correlation, southern hemisphere, tree-ring chronologies, forestry, antarctic oscillation, complexity, correlation, evergreen tree, principal component analysis, temporal variation, timescale, twentieth century, andes, patagonia, nothofagus pumilio
High Impact Weather Events in the AndesPoveda, Germán; Espinoza, Jhan Carlo; Zuluaga, Manuel D.; Solman, Silvina A.; Garreaud, René; van Oevelen, Peter J.Agua y Extremos2020.010.3389/feart.2020.00162Frontiers in Earth Science2296-6463 Reuters ISIdeforestation, economics, extreme weather, land use, precipitation (meteorology), storms, tropics, water pollution, weather information services, extratropical, extreme precipitation events, extreme weather events, high mountains, land-use change, mesoscale convective system, research gaps, weather events, climate change
Geo-climatic hazards in the eastern subtropical Andes: distribution, climate drivers and trendsVergara, Iván; Moreiras, Stella M.; Araneo, Diego; Garreaud, RenéAgua y Extremos2020.010.5194/nhess-20-1353-2020Abstract. Detecting and understanding historical changes in the frequency of geo-climatic hazards (G-CHs) is crucial for the quantification of current hazards and project them into the future. Here we focus in the eastern subtropical Andes (32–33∘ S), using meteorological data and a century-long inventory of 553 G-CHs triggered by rainfall or snowfall. We first analyse their spatio-temporal distributions and the role of climate variability in the year-to-year changes in the number of days per season with G-CHs. Precipitation is positively correlated with the number of G-CHs across the region and year-round; mean temperature is negatively correlated with snowfall-driven hazards in the western (higher) half of the study region during winter and with rainfall-driven hazards in the eastern zone during summer. The trends of the G-CH frequency since the mid-20th century were calculated, paying attention to their non-systematic monitoring. The G-CH series for the different triggers, zones and seasons were generally stationary. Nonetheless, there is a small positive trend in rainfall-driven G-CHs in the eastern zone during summer, congruent with a rainfall increase there. We also found a decrease in snowfall-driven G-CHs in the western zone from the late 1990s onwards, most likely due to a reduction in winter precipitation rather than to an increase in temperature.Natural Hazards and Earth System Sciences1684-9981 Reuters ISIclimate conditions, detection method, precipitation intensity, seasonal variation, snow, spatiotemporal analysis, subtropical region, trend analysis, andes
Thermo- and physicochemical properties of native and exotic forest species of Valparaíso, Chile, as essential information for fire risk managementGuerrero, Fabián; Toledo, Mario; Ripoll, Nicolás; Espinoza, Lorena; Morales, Rodrigo; Muñoz, Ariel; Taborga, Lautaro; Carrasco, YulianAgua y Extremos2020.010.1071/WF19086Wildfires in the Valparaı́so region (Chile) account for one of the main threats to local biodiversity, ecosystem services and infrastructure. This study focused on producing an initial record of thermo- and physicochemical properties of local forest species. For this purpose, leaf samples of species found in the Peñuelas Lake National Reserve, namely Pinus radiata, Eucalyptus globulus, Acacia dealbata, Quillaja saponaria and Cryptocarya alba, were collected and analysed. Higher and lower heating value, flash point, density and moisture content tests were performed for each sample. Overall results showed that lower heating values measured for both native and exotic species could indicate a high energy release source in wildfires. However, differences in the flash point between species indicated that C. alba and E. globulus had a lower ignition resistance than other species tested, possibly due to a lower flash point. In contrast, Q. saponaria and A. dealbata had the highest flash point for native and exotic species respectively. Finally, all presented data and procedures were aimed at establishing a foundation for a national database of critical forest species properties to be used in wildfire simulation tools. This database will enhance forest fire management effectiveness in Chile.International Journal of Wildland Fire1049-8001 Reuters ISIcalorific value, cryptocarya alba, flash point, forest fires, forest fuel, moisture content, quillaja saponaria, wildfires
Environmental costs of water transfersVargas, Cristian A.; Garreaud, Rene; Barra, Ricardo; Vásquez-Lavin, Felipe; Saldías, Gonzalo S.; Parra, OscarAgua y Extremos2020.010.1038/s41893-020-0526-5Nature Sustainability2398-9629 Reuters ISI
Raco Wind at the Exit of the Maipo Canyon in Central Chile: Climatology, Special Observations, and Possible MechanismsMuñoz R.; Armi, Laurence; Rutllant, José A.; Falvey, Mark; Whiteman, C. David; Garreaud, René; Arriagada, Andrés; Flores, Federico; Donoso, NicolásAgua y Extremos2020.010.1175/JAMC-D-19-0188.1Raco is the local name given to a strong (gusts up to 17 m s −1 ), warm, and dry down-valley wind observed at the exit of the Maipo River Canyon in central Chile. Its climatology is documented based on eight years of surface measurements near the canyon exit together with a more complete characterization of its structure during an intensive observational period (IOP) carried out in July 2018. Raco winds occur in the cold season under well-defined synoptic conditions, beginning abruptly at any time during the night, reaching maximum hourly averages around 10 m s −1 , and terminating around noon with the onset of afternoon westerly up-valley winds. About 25% of the days in May–August have more than six raco hours between 0100 and 1200 LT, and raco episodes last typically 1–2 days. The sudden appearance of raco winds at the surface can be accompanied by conspicuous warming (up to 10°C) and drying (up to 3 g kg −1 ). Raco winds are associated with a strong along-canyon pressure gradient, a regional pressure fall, and clear skies. During the IOP, radiosondes launched from both extremes of the canyon exit corridor showed a nocturnal easterly jet at 700 m AGL that occasionally descended rapidly to the surface, producing the raco. Transects along the canyon performed with a mobile ceilometer revealed a sharp frontlike feature between the cold pool over the Santiago Valley and the raco-affected conditions in the Maipo Canyon. Possible factors producing the easterly jet aloft and its occasional descent toward the surface are discussed, and a gap-wind mechanism is postulated to be at work.Journal of Applied Meteorology and Climatology1558-8424, 1558-8432 Reuters ISIclimatology, landforms, meteorological instruments, surface measurement, central chile, clear sky, cold season, intensive observational periods, possible mechanisms, synoptic conditions, up-valley winds, valley winds, wind, canyon, climatology, gust, jet stream, pressure gradient, chile, maipo river
First snow, glacier and groundwater contribution quantification in the upper Mendoza River basin using stable water isotopesCrespo, Sebastián; Fernandoy, Francisco; Cara, Leandro; Klarian, Sebastián; Lavergne, CélineAgua y Extremos10.1080/10256016.2020.1797713The Mendoza River streamflow, South America (∼32 °S), derives almost exclusively from winter snow precipitation falling in the Andes. Almost 70% of the water feeding the river originates in the Cordillera Principal geological province. In addition to the snow that precipitates in this area, there are 951 cryoforms providing meltwater to the upper catchment. Given the high inter-annual variability of snowfall and the megadrought affecting the region since 2010, it is crucial to quantify the contribution from different water sources buffering the Mendoza River runoff. Combining instrumental records of streamflow from glaciers and rivers, meteorological data, remote sensing of snow-covered areas and ionic and stable isotope analysis of different water sources, this study attempts to understand the hydrological contribution of different water sources to the basin. We demonstrated for the first time the relevance of different water sources in addition to snow in a dry period. During the melting season, 65% of the streamwaters originated from the glaciers (i.e. 50 and 15% from glaciers and rock glaciers, respectively), representing a higher proportion compared to snowmelt (17%). Groundwater input showed relatively large contributions, averaging 18%. This work offers information to develop adaptation strategies for future climate change scenarios in the region.Isotopes in Environmental and Health Studies1025-6016, 1477-2639 Reuters ISIclimate change, glacier dynamics, groundwater, hydrogen isotope, oxygen isotope, rock glacier, snow cover, stable isotope, streamflow, water quality, andes, argentina, mendoza, mendoza river, deuterium, ground water, isotope, oxygen, snow, altitude, chemistry, chile, climate change, environmental monitoring, hydrology, ice cover, procedures, river, season, water cycle, altitude, chile, climate change, deuterium, environmental monitoring, groundwater, hydrology, ice cover, isotopes, oxygen isotopes, rivers, seasons, snow, water cycle
Where Does the Chilean Aconcagua River Come from? Use of Natural Tracers for Water Genesis Characterization in Glacial and Periglacial EnvironmentsCrespo, Sebastián; Lavergne, Céline; Fernandoy, Francisco; Muñoz, Ariel; Cara, Leandro; Olfos-Vargas, SimónAgua y Extremos10.3390/w12092630The Aconcagua river basin (Chile, 32 °S) has suffered the effects of the megadrought over the last decade. The severe snowfall deficiency drastically modified the water supply to the catchment headwaters. Despite the recognized snowmelt contribution to the basin, an unknown streamflow buffering effect is produced by glacial, periglacial and groundwater inputs, especially in dry periods. Hence, each type of water source was characterized and quantified for each season, through the combination of stable isotope and ionic analyses as natural water tracers. The δ18O and electric conductivity were identified as the key parameters for the differentiation of each water source. The use of these parameters in the stable isotope mixing “simmr” model revealed that snowmelt input accounted 52% in spring and only 22–36% during the rest of the year in the headwaters. While glacial supply contributed up to 34%, both groundwater and periglacial exhibited a remarkable contribution around 20% with some seasonal variations. Downstream, glacial contribution averaged 15–20%, groundwater seasonally increased up to 46%, and periglacial input was surprisingly high (i.e., 14–21%). The different water sources contribution quantification over time for the Aconcagua River reported in this work provides key information for water security in this territory.Water2073-4441 Reuters ISIcatchments, glacial geology, groundwater, isotopes, rivers, snow melting systems, water supply, buffering effect, ionic analysis, natural tracers, natural waters, seasonal variation, stable isotopes, water genesis, water security, tracers, catchment, ionic composition, river basin, seasonal variation, snowmelt, stable isotope, streamflow, aconcagua river, chile, valparaiso [chile]
Hydroclimate of the Andes Part I: Main Climatic FeaturesEspinoza, Jhan Carlo; Garreaud, René; Poveda, Germán; Arias, Paola A.; Molina-Carpio, Jorge; Masiokas, Mariano; Viale, Maximiliano; Scaff, LuciaAgua y Extremos2020.010.3389/feart.2020.00064The Andes is the longest cordillera in the world and extends from northern South America (11°N) to the southern tip of the continent (53°S). The Andes runs through seven countries and is characterized by a wide variety of ecosystems strongly related to the contrasting climate over its eastern and western sides and along its latitudinal extension. In fact, the tropical Andes is the most biodiverse region on Earth. Currently, this region faces the highest potential impact of climate change, which could affect food security and water supplies for about 90 million people. From a scientific and societal view, the Andes present specific challenges because of its unique landscape and the fragile equilibrium between the growing population and its environment. In this manuscript, we provide an updated review of the most relevant scientific literature regarding the hydroclimate of the Andes. This review paper is presented in two parts. Part I is dedicated to summarize the scientific knowledge about the main climatic features of the Andes, with emphasis on mean large-scale atmospheric circulation, the Andes-Amazon hydroclimate interconnections, and the regular cycles of precipitation, including the most characteristic diurnal and annual cycles of precipitation. Part II, which is also included in the research topic “Connecting Mountain Hydroclimate Through the American Cordilleras”, focuses on hydroclimate variability of the Andes at a sub-continental scale.Frontiers in Earth Science2296-6463 Reuters ISIatmospheric pressure, biodiversity, earth (planet), atmospheric circulation, climatic features, continental scale, research topics, scientific knowledge, scientific literature, southern oscillation, water security, climate change
Extreme sea levels at Rapa Nui (Easter Island) during intense atmospheric riversCarvajal, Matías; Winckler, Patricio; Garreaud, René; Igualt, Felipe; Contreras-López, Manuel; Averil, Pamela; Cisternas, Marco; Gubler, Alejandra; Breuer, Wolfgang A.Agua y Extremos2021.010.1007/s11069-020-04462-2In addition to the tsunami hazard posed by distant great earthquakes, Rapa Nui (Easter Island), in the Southeast Pacific Ocean, is exposed to frequent and intense coastal storms. Here, we use sea-level records and field surveys guided by video and photographic footage to show that extreme sea levels at Rapa Nui occur much more frequent than previously thought and thus constitute an unrecognized hazard to the inland’s maritime supply chain. We found that extreme sea-level events, including the two most extreme (March 5th and May 5th, 2020) in our 17-month-long analyzed period (from January 1st, 2019, to May 31st, 2020), resulted from constructive superpositions of seiches on the shelf, storm surges and high tides. By further analyzing time series of atmospheric and wind-generated wave data, we conclude that these extreme sea levels are ultimately driven by the breaking of large waves near the coastline (i.e., wave setup), with lesser contribution of barometric setup and even less of wind setup. We also propose that these large waves were mainly generated from strong, long-lasting, NW winds associated with intense atmospheric rivers (long, narrow regions in the atmosphere that transport abundant water vapor) passing over Rapa Nui. Given that the intensity of atmospheric rivers and sea level are thought to increase as climate changes, a deeper understanding of the relation between meteorological and oceanographic processes at Rapa Nui is strongly needed.Natural Hazards0921-030X Reuters ISIatmospheric dynamics, extreme event, field survey, hazard assessment, photography, sea level, sea level change, seiche, storm surge, time series, tsunami, vulnerability, water vapor, wind wave, easter island, pacific ocean, pacific ocean (southeast)
Future Changes in the Free Tropospheric Freezing Level and Rain–Snow Limit: The Case of Central ChileMardones, Piero; Garreaud, René D.Agua y Extremos2020.010.3390/atmos11111259The freezing level in the free troposphere often intercepts the terrain of the world’s major mountain ranges, creating a rain–snow limit. In this work, we use the free tropospheric height of the 0 °C isotherm (H0) as a proxy of both levels and study its distribution along the western slope of the subtropical Andes (30°–38° S) in present climate and during the rest of the 21st century. This portion of the Andes corresponds to central Chile, a highly populated region where warm winter storms have produced devastating landslides and widespread flooding in the recent past. Our analysis is based on the frequency distribution of H0 derived from radiosonde and surface observations, atmospheric reanalysis and climate simulations. The future projections primarily employ a scenario of heavy greenhouse gasses emissions (RCP8.5), but we also examine the more benign RCP4.5 scenario. The current H0 distribution along the central Chile coast shows a gradual decrease southward, with mean heights close to 2600 m ASL (above sea level) at 30 °C S to 2000 m ASL at 38° S for days with precipitation, about 800 m lower than during dry days. The mean value under wet conditions toward the end of the century (under RCP8.5) is close to, or higher than, the upper quartile of the H0 distribution in the current climate. More worrisome, H0 values that currently occur only 5% of the time will be exceeded in about a quarter of the rainy days by the end of the century. Under RCP8.5, even moderate daily precipitation can increase river flow to levels that are considered hazardous for central Chile.Atmosphere2073-4433 Reuters ISIfreezing, rain, sea level, snow, storms, atmospheric reanalysis, climate simulation, daily precipitations, free troposphere, frequency distributions, future projections, mountain ranges, surface observation, troposphere, climate change, cmip, flooding, freezing, future prospect, troposphere, andes, chile
The Chilean Tornado Outbreak of May 2019: Synoptic, mesoscale, and historical contextsVicencio, José; Rondanelli, Roberto; Campos, Diego; Valenzuela, Raúl; Garreaud, René; Reyes, Alejandra; Padilla, Rodrigo; Abarca, Ricardo; Barahona, Camilo; Delgado, Rodrigo; Nicora, GabrielaZonas Costeras; Agua y Extremos2020.010.1175/BAMS-D-19-0218.1Capsule An unprecedented tornado outbreak occurred in Southern Chile, with at least seven tornadoes reported over a period of 24 hours, causing substantial damage, dozens of injuries, and one fatality.Bulletin of the American Meteorological Society0003-0007, 1520-0477 Reuters ISIpotential energy, storms, anecdotal evidences, convective available potential energies, lightning datum, low-level winds, mid-latitude storms, tornado outbreak, vorticity generation, western south america, tornadoes
Extreme Drought Affects Visitation and Seed Set in a Plant Species in the Central Chilean Andes Heavily Dependent on Hummingbird PollinationArroyo, Mary T. K.; Robles, Valeria; Tamburrino, Ítalo; Martínez-Harms, Jaime; Garreaud, René D.; Jara-Arancio, Paola; Pliscoff, Patricio; Copier, Ana; Arenas, Jonás; Keymer, Joaquín; Castro, KiaraAgua y Extremos2020.010.3390/plants9111553Rising temperatures and increasing drought in Mediterranean-type climate areas are expected to affect plant–pollinator interactions, especially in plant species with specialised pollination. Central Chile experienced a mega drought between 2010 and 2020 which reached an extreme in the austral summer of 2019–2020. Based on intensive pollinator sampling and floral studies we show that the subalpine form of Mutisia subulata (Asteraceae) is a specialised hummingbird-pollinated species. In a two-year study which included the severest drought year, we quantified visitation frequency, flower-head density, flower-head visitation rates, two measures of floral longevity, nectar characteristics and seed set and monitored climatic variables to detect direct and indirect climate-related effects on pollinator visitation. Flower-head density, nectar standing crop and seed set were significantly reduced in the severest drought year while nectar concentration increased. The best model to explain visitation frequency included flower-head density, relative humidity, temperature, and nectar standing crop with highly significant effects of the first three variables. Results for flower-head density suggest hummingbirds were able to associate visual signals with reduced resource availability and/or were less abundant. The negative effect of lower relative humidity suggests the birds were able to perceive differences in nectar concentration. Reduced seed set per flower-head together with the availability of far fewer ovules in the 2019–2020 austral summer would have resulted in a major reduction in seed set. Longer and more intense droughts in this century could threaten local population persistence in M. subulata.Plants2223-7747 Reuters ISIcentral chile, extreme drought, floral longevity, floral resources, hummingbird-pollination, mutisia subulata, oreotrochilus leucopleurus, seed set, visitation rates
Connection between Antarctic Ozone and Climate: Interannual Precipitation Changes in the Southern HemisphereDamiani, Alessandro; Cordero, Raul R.; Llanillo, Pedro J.; Feron, Sarah; Boisier, Juan P.; Garreaud, Rene; Rondanelli, Roberto; Irie, Hitoshi; Watanabe, ShingoZonas Costeras; Agua y Extremos2020.010.3390/atmos11060579In this study, we explored the connection between anomalies in springtime Antarctic ozone and all-year precipitation in the Southern Hemisphere by using observations from 1960–2018 and coupled simulations for 1960–2050. The observations showed that this correlation was enhanced during the last several decades, when a simultaneously increased coupling between ozone and Southern Annular Mode (SAM) anomalies became broader, covering most of the following summer and part of the previous winter. For eastern Australia, the ozone–precipitation connection shows a greater persistence toward the following summer than for other regions. On the other hand, for South America, the ozone–precipitation correlation seems more robust, especially in the early summer. There, the correlation also covers part of the previous winter, suggesting that winter planetary waves could affect both parameters. Further, we estimated the sensitivity of precipitation to changes in Antarctic ozone. In both observations and simulations, we found comparable sensitivity values during the spring–summer period. Overall, our results indicate that ozone anomalies can be understood as a tracer of stratospheric circulation. However, simulations indicate that stratospheric ozone chemistry still contributes to strengthening the interannual relationship between ozone and surface climate. Because simulations reproduced most of the observed connections, we suggest that including ozone variability in seasonal forecasting systems can potentially improve predictions.Atmosphere2073-4433 Reuters ISIozone layer, coupled simulation, precipitation change, seasonal forecasting, sensitivity values, southern annular mode, southern hemisphere, stratospheric circulations, stratospheric ozone chemistry, ozone, annual variation, anomaly, atmospheric chemistry, computer simulation, ozone, precipitation (climatology), regional climate, southern hemisphere, antarctica
Daily and seasonal variation of the surface temperature lapse rate and 0°C isotherm height in the western subtropical AndesIbañez, María; Gironás, Jorge; Oberli, Christian; Chadwick, Cristián; Garreaud, René D.Agua y Extremos2020.010.1002/joc.6743International Journal of Climatology0899-8418, 1097-0088 Reuters ISIcatchments, floods, isotherms, risk assessment, risk perception, runoff, surface properties, tropics, hydrological modelling, inter-day variations, mountainous basins, seasonal variation, surface air temperatures, surface temperatures, temperature inversions, temporal variation, atmospheric temperature, diurnal variation, mountain environment, mountain region, seasonal variation, sensor, surface temperature, warming, andes, chile
Seasonal precipitation in South Central Chile: trends in extreme events since 1900González-Reyes, Álvaro; Jacques-Coper, Martin; Muñoz, Ariel AndresZonas Costeras; Agua y Extremos2020.010.20937/ATM.52871We study a regional precipitation time series, built upon seven meteorological records from South Central Chile (SCC; 37° - 42°S), which together cover the period 1900 - 2019. As a first objective, we investigated changes in the return period (RP) of dry ( P80) seasonal extreme events of precipitation (SEE), for each season. We observed a reduction in the RP of wet SEE during 1900 - 1950 in all seasons. Contrarily, the dry SEE RP shows a reduction from 1950 to the present in all seasons. This phenomenon is noteworthy since 1900 for summer and winter, and since 1930 for autumn. Spring registers a constant RP value from 1990 onwards. As a second objective, we study possible relationships between seasonal precipitation variability and climate modes, such as the Southern Annular Mode (SAM) and the Tripolar Index (TPI) of sea surface temperature (SST) over the Pacific Ocean. Summer and autumn precipitation register a significant negative correlation with SAM activity at interannual and decadal scales, while winter and spring precipitation show a significant positive correlation with SST variability over multiple regions of the Pacific Ocean (including the tropics and New Zealand) and the Southern Ocean (Amundsen-Bellingshausen Sea). Finally, we confirm that SAM strongly modulates precipitation in SCC, especially in autumn, and that SEE variability in SCC is considerably characterized by climate modes of tropical and extra-tropical origin.Atmósfera Reuters ISIextreme seasonal precipitation events, south-central chile, southern annular mode (sam), tripole index of sea surface temperature of the pacific ocean (tpi)
Transformation of social capital during and after a disaster event: the cases Chañaral and Diego de Almagro, Atacama Region, ChileCastro-Correa, Carmen-Paz; Aldunce Ide, Paulina; Wyndham Vásquez, Katherine; Mena Maldonado, Dania; Pérez Tello, SoniaAgua y Extremos2020.010.1007/s11069-020-04091-9This article analyzes the impact of socio-natural disasters on social capital at a local level, studying the cases of the communities of Chañaral and Diego de Almagro after the flooding and mudflow disasters of 2015. Specifically, we explore different dynamics of social capital in the response to the emergency, recovery and reconstruction stages, exploring its role in strengthening adaptation and resilience capacities for disaster risk reduction. Through the qualitative analysis of semi-structured interviews with survivors of the disaster, we explore the nature and role of social trust and its influence on the formation and consolidation of bonding, bridging and linking social capital in the context of disaster is analyzed. The results unpack the role of social capital in the response, recovery and reconstruction processes after a disaster event, which directly influences the development and consolidation of capacities for community adaptation, highlighting the role of trust for the strengthening of resilience. Likewise, the article provides details about the role of institutions and authorities in the consolidation of bridging and linking social capital, which requires the generation of formal and fluid communication channels that allow for the creation of trust, not only among the members of the community, but between the community and the institutions and authorities.Natural Hazards0921-030X, 1573-0840 Reuters ISIadaptive management, consolidation, disaster management, flooding, local participation, mudflow, qualitative analysis, social capital, atacama, chanaral island, chile, diego de almagro island, magallanes
Fire history in Andean Araucaria–Nothofagus forests: coupled influences of past human land-use and climate on fire regimes in north-west PatagoniaGonzález, M. E.; Muñoz, A. A.; González-Reyes, A.; Christie, D. A.; Sibold, J.Cambio de Uso de Suelo; Agua y Extremos2020.010.1071/WF19174International Journal of Wildland Fire1049-8001 Reuters ISIclimate variability, dendroecology, el niño southern oscillation, native americans, southern annular mode, tree-rings
Local Perceptions of Fires Risk and Policy Implications in the Hills of Valparaíso, ChileSapiains, Rodolfo; Ugarte, Ana María; Aldunce, Paulina; Marchant, Germant; Romero, Javier Alberto; González, Mauro E.; Inostroza-Lazo, ValentinaCambio de Uso de Suelo; Agua y Extremos; Gobernanza e Interfaz Ciencia y Política10.3390/su12104298Climate change is increasing the occurrence of natural disasters worldwide, and more frequent and intense fires represent one of the most destructive expressions of this trend. Chile is highly vulnerable to climate change, and fires are a recurrent phenomenon affecting many people each year. To reduce fire risk, the Intergovernmental Panel on Climate Change (IPCC) suggests reducing both exposure and vulnerability through multiple initiatives, which demand increased community engagement. In such a context, this study explores local perceptions of fire in a sample of inhabitants in a wildland-urban interface (WUI) in Valparaiso, a city that is affected by numerous fires each year. The ultimate goal was to identify psychological and community factors that should be taken into consideration to develop prevention plans and safer environments for people living in a context of poverty and social inequity. Using a qualitative approach, 28 interviews were conducted and analyzed following grounded theory principles. Results identified multiple causes, impacts, and characteristics of the problem perceived by people who permanently cohabit with fire risk, showing that for many of them, fire risk is not about the probability of occurrence of a disaster, but a question about when and how the next fire will happen. However, in such a complex scenario, psychological, community, and structural barriers deter people from implementing more effective actions. Conversely, in emergency situations, such barriers are irrelevant and cooperative actions prevail, suggesting the existence of resources and capacities within the community that could lessen exposure and vulnerability if activated on a day-to-day basis. Overall, reducing fire risk cannot be achieved by local communities alone nor without their support. To build, maintain, and consolidate fire prevention actions, it is critical to activate community strengths and cooperation and engage the resources and management capacity of local governments.Sustainability2071-1050 Reuters ISIfire management, intergovernmental panel on climate change, local government, local planning, natural disaster, policy implementation, probability, qualitative analysis, risk assessment, vulnerability, valparaiso
Recent Near-surface Temperature Trends in the Antarctic Peninsula from Observed, Reanalysis and Regional Climate Model DataBozkurt, D.; Bromwich, D. H.; Carrasco, J; Hines, Keith M.; Maureira, J. C.; Rondanelli, R.Zonas Costeras; Agua y Extremos2020.010.1007/s00376-020-9183-xThis study investigates the recent near-surface temperature trends over the Antarctic Peninsula. We make use of available surface observations, ECMWF’s ERA5 and its predecessor ERA-Interim, as well as numerical simulations, allowing us to contrast different data sources. We use hindcast simulations performed with Polar-WRF over the Antarctic Peninsula on a nested domain configuration at 45 km (PWRF-45) and 15 km (PWRF-15) spatial resolutions for the period 1991-2015. In addition, we include hindcast simulations of KNMI-RACMO21P obtained from the CORDEX-Antarctica domain (~50 km) for further comparisons. Results show that there is a marked windward warming trend except during summer. This windward warming trend is particularly notable in the autumn season and likely to be associated with the recent deepening of the Amundsen/Bellingshausen Sea low and warm advection towards the Antarctic Peninsula. On the other hand, an overall summer cooling is characterized by the strengthening of the Weddell Sea low as well as an anticyclonic trend over the Amundsen Sea accompanied by northward winds. The persistent cooling trend observed at the Larsen Ice Shelf station is not captured by ERA-Interim, whereas hindcast simulations indicate that there is a clear pattern of windward warming and leeward cooling. Furthermore, larger temporal correlations and lower differences exhibited by PWRF-15 illustrate the existence of the added value in the higher spatial resolution simulation.Advances in Atmospheric Sciences0256-1530, 1861-9533 Reuters ISIadded value, amundsen/bellingshausen sea, cloud computing, dynamical downscaling, reanalysis, temperature trend, weddell sea, 宋米荣
An early Holocene westerly minimum in the southern mid-latitudesMoreno, P.I; Henríquez, W.I.; Pesce, O.H.; Henríquez, C.A.; Fletcher, M.S.; Garreaud, R.D.; Villa-Martínez, R.P.Agua y Extremos2021.010.1016/j.quascirev.2020.106730An important coupled ocean-atmospheric system in the mid- and high latitudes involves the Southern Westerly Winds (SWW) and the Southern Ocean (SO), which controls climate in the southernmost third of the world, deep water formation, and ventilation of CO2 from the deep ocean. Most studies have examined its role as a driver of atmospheric CO2 concentrations during glacial terminations, but very few have investigated its influence during the Holocene, i.e. the current interglacial. A fundamental problem, however, is resolving whether the SWW strength increased or declined during the early Holocene (∼11.5–7.5 ka, ka = 1000 cal yr BP) in sectors adjacent to the Drake Passage. Here we assess past changes in SWW influence over the last ∼17,000 years using terrestrial paleoclimate records from southwestern Patagonia (∼52°S). We detect a zonally symmetric Early Holocene Westerly Minimum which diminished wind stress and upwelling on the SO, contributing to a contemporary decline in atmospheric CO2 concentrations and enrichment in the stable carbon isotope ratio of atmospheric CO2 (δ13Catm). Our mid-latitude data also indicate a shift to strong SWW influence at ∼7.5 ka which correlates with a sustained increase in atmospheric CO2 and halt in the δ13Catm rise, suggesting enhancement of high-latitude ocean ventilation by an invigorated SWW-SO coupled system.Quaternary Science Reviews0277-3791 Reuters ISIoceanography, atmospheric systems, co2 concentration, deep-water formation, glacial terminations, ocean ventilations, paleoclimate records, southern westerly winds, stable carbon isotope ratio, carbon dioxide, atmosphere-ocean coupling, carbon isotope ratio, concentration (composition), historical record, holocene, midlatitude environment, paleoclimate, stable isotope, upwelling, westerly, drake passage, patagonia, southern ocean
Modulation of Fire Regimes by Vegetation and Site Type in Southwestern Patagonia Since 13 kaMoreno, Patricio I.; Vilanova, Isabel; Villa-Martínez, Rodrigo P.; Francois, Jean P.Agua y Extremos2018.010.3389/fevo.2018.00034The degree to which vegetation and site type have influenced fire regimes through the Holocene has not been investigated in detail in the temperate ecosystems of southern Patagonia. Here we present a first attempt using a paired-basin approach to study the evolution of fire regimes in sectors dominated by humid Nothofagus forests and the xeric Patagonian steppe in the Magallanes region of Chilean Patagonia (51°S). We analyzed sediment cores from two small lakes and a bog located within the same climate zone on opposite sides of the forest-steppe ecotone, ~28 km apart. The position of this biological boundary east of the Andes is controlled by the strength and position of the southern westerly winds, which constitute the sole source of precipitation throughout western Patagonia. Our results indicate that fires have occurred in the study region repeated times over the last ~13,000 years at bi- and tridecadal timescales. Sectors currently dominated by Patagonian steppe feature high frequency and low magnitude of local fires, and vice versa in humid forests. Climate-driven expansion of Nothofagus scrubland/woodland into steppe environments over the last ~4,200 years increased the magnitude and lowered the frequency of fire events, culminating with peak Nothofagus abundance, fire magnitude and frequency during the last millennium. We also detect divergences between lake-based vs. bog-based paleofire histories among paired sites located within the Patagonian steppe, ~12 km apart, which we attribute to local burning of the bog at times of lowered water table. This divergence suggests to us that bog-based vegetation and fire histories exacerbate a local, azonal, signal blurring extra-local or regional regimes, thus accounting for some discrepancies in the Quaternary paleovegetation/paleoclimate literature of southern Patagonia.Frontiers in Ecology and Evolution2296-701X Reuters ISIfire regime, lake sediments, paleoclimate, patagonia, vegetation dynamics
Multidecadal environmental pollution in a mega-industrial area in central Chile registered by tree ringsMuñoz, Ariel A.; Klock-Barría, Karin; Sheppard, Paul R.; Aguilera-Betti, Isabella; Toledo-Guerrero, Isadora; Christie, Duncan A.; Gorena, Tamara; Gallardo, Laura; González-Reyes, Álvaro; Lara, Antonio; Lambert, Fabrice; Gayo, Eugenia; Barraza, Francisco; Chávez, Roberto O.Ciudades Resilientes; Agua y Extremos2019.010.1016/j.scitotenv.2019.133915Science of The Total Environment0048-9697 Reuters ISIair quality, aluminum alloys, pollution control, trace elements, trees (mathematics), baseline, dendrochemistry, industrial pollution, macrocarpa, trace metal, forestry, aluminum, arsenic, cadmium, chromium, cobalt, copper, iron, lead, molybdenum, silver, trace metal, vanadium, zinc, anthropogenic source, concentration (composition), decadal variation, dendrochronology, environmental change, soil pollution, soil quality, trace metal, tree ring, air monitoring, air pollution, air quality, article, biochemistry, chemical composition, chile, comparative study, controlled study, cupressus, cupressus macrocarpa, dendrochemistry, environmental impact, geographic distribution, human activities, industrial area, plant structures, priority journal, temporal analysis, tree ring, chemistry, environmental monitoring, industry, pollution, procedures, tree, chile, cupressus macrocarpa, chile, environmental monitoring, environmental pollution, industry, trees
Holocene glacier fluctuations in Patagonia are modulated by summer insolation intensity and paced by Southern Annular Mode-like variabilityReynhout, Scott A.; Sagredo, Esteban A.; Kaplan, Michael R.; Aravena, Juan Carlos; Martini, Mateo A.; Moreno, Patricio I.; Rojas, Maisa; Schwartz, Roseanne; Schaefer, Joerg M.Agua y Extremos; Gobernanza e Interfaz Ciencia y Política2019.010.1016/j.quascirev.2019.05.029Alpine glaciers are sensitive indicators of changes in climate, and their ubiquity in mountainous regions make them valuable proxies for terrestrial climate reconstructions worldwide. However, the timing and extent of glacier change across the South American mid-latitudes through the Holocene are still poorly constrained relative to their counterparts in the Northern Hemisphere. Here we report a new 10Be surface exposure-based chronology of moraines recording a series of progressively less-extensive glacier advances of Glaciar Torre (Argentina, 49.3°S/73.0°W) since the Last Glacial Maximum, with expansions culminating at 17,600 ± 900, 13,500 ± 500, 9700 ± 400, 6900 ± 200, 6100 ± 300, 4500 ± 200, and 530 ± 60 yr BP. The declining magnitude of Holocene glacier expansions parallels a gradual rise in local summer insolation intensity during the Holocene, while individual advances occurred during inferred negative Southern Annular Mode (SAM)-like states at centennial to millennial timescales. These observations suggest that (i) summer insolation intensity modulated antiphased trends in glacier extent in the polar hemispheres during the Holocene, and that (ii) centennial-scale ‘SAM-like’ temperature and precipitation anomalies paced glacier fluctuations throughout Patagonia. Given the persistence of the inferred ’SAM-like’ anomalies throughout the Holocene, the modern measured trend towards positive SAM index conditions could mark the onset of a fundamental shift in the climate of the Southern Hemisphere midlatitudes that warrants consideration in projections of future climate.Quaternary Science Reviews0277-3791 Reuters ISIexpansion, geomorphology, glacial geology, cosmogenic isotopes, glacial, glaciation, holocenes, paleoclimatology, south america, southern annular mode, incident solar radiation, chronology, geomorphology, glacier advance, holocene, insolation, last glacial maximum, midlatitude environment, mountain region, paleoclimate, precipitation (climatology), reconstruction, southern hemisphere, summer, argentina, patagonia
The Central Chile Mega Drought (2010–2018): A climate dynamics perspectiveGarreaud, R.; Boisier, J. P.; Rondanelli, R.; Montecinos, A.; Sepúlveda, H.; Veloso‐Aguila, D.Zonas Costeras; Agua y Extremos2020.010.1002/joc.6219Central Chile, home to more than 10 million inhabitants, has experienced an uninterrupted sequence of dry years since 2010 with mean rainfall deficits of 20–40%. The so‐called Mega Drought (MD) is the longest event on record and with few analogues in the last millennia. It encompasses a broad area, with detrimental effects on water availability, vegetation and forest fires that have scaled into social and economical impacts. Observations and reanalysis data reveal that the exceptional length of the MD results from the prevalence of a circulation dipole‐hindering the passage of extratropical storms over central Chile—characterized by deep tropospheric anticyclonic anomalies over the subtropical Pacific and cyclonic anomalies over the Amundsen–Bellingshausen Sea. El Niño Southern Oscillation (ENSO) is a major modulator of such dipole, but the MD has occurred mostly under ENSO‐neutral conditions, except for the winters of 2010 (La Niña) and 2015 (strong El Niño). Climate model simulations driven both with historical forcing (natural and anthropogenic) and observed global SST replicate the south Pacific dipole and capture part of the rainfall anomalies. Idealized numerical experiments suggest that most of the atmospheric anomalies emanate from the subtropical southwest Pacific, a region that has experienced a marked surface warming over the last decade. Such warming may excite atmospheric Rossby waves whose propagation intensifies the circulation pattern leading to dry conditions in central Chile. On the other hand, anthropogenic forcing (greenhouse gases concentration increase and stratospheric ozone depletion) and the associated positive trend of the Southern Annular Mode also contribute to the strength of the south Pacific dipole and hence to the intensity and longevity of the MD. Given the concomitance of the seemingly natural (ocean sourced) and anthropogenic forcing, we anticipate only a partial recovery of central Chile precipitation in the decades to come.International Journal of Climatology0899-8418 Reuters ISIatmospheric pressure, climate change, deforestation, drought, greenhouse gases, mechanical waves, oceanography, ozone layer, rain, tropics, anthropogenic forcing, anticyclonic anomalies, chile, climate model simulations, enso, numerical experiments, south america, stratospheric ozone depletion, climate models, antarctic oscillation, anthropogenic effect, atmospheric dynamics, climate change, climate forcing, drought, el nino-southern oscillation, pacific decadal oscillation, precipitation (climatology), rossby wave, amundsen sea, bellingshausen sea, chile, pacific ocean, pacific ocean (south), pacific ocean (subtropical), southern ocean
The glass half-empty: climate change drives lower freshwater input in the coastal system of the Chilean Northern PatagoniaAguayo, Rodrigo; León-Muñoz, Jorge; Vargas-Baecheler, José; Montecinos, Aldo; Garreaud, René; Urbina, Mauricio; Soto, Doris; Iriarte, José LuisAgua y Extremos2019.010.1007/s10584-019-02495-6Oceanographic conditions in coastal Chilean northern Patagonia (41–46°S) are strongly influenced by freshwater inputs. Precipitation and streamflow records have shown a marked decrease in this area during the last decades. Given this hydro-climatic scenario, we evaluated the hydrological sensitivity driven by climate change in the Puelo River (average annual streamflow = 640 m³ s⁻¹), one of the most important sources of freshwater in the fjords and inland seas of Chile’s Northern Patagonia. A lumped hydrological model was developed to evaluate the potential impacts of climate change under the Representative Concentration Pathways (RCP) 2.6, 4.5, and 8.5 scenarios in the near future (2030–2060) using the delta change method based on 25 General Circulation Models. The model was fed by local hydro-meteorological data and remote sensors, simulating well the magnitude and seasonality of Puelo River streamflow. Considering the Refined Index of Agreement (RIA), the model achieved a high performance in the calibration (RIA = 0.79) and validation stages (RIA = 0.78). Under the RCP 8.5 scenario (multi-model mean), the projections suggest that the annual input of freshwater from the Puelo River to the Reloncaví Fjord would decrease by − 10% (1.6 km³ less freshwater); these decreases would mainly take place in summer (~ − 20%) and autumn (~ − 15%). The recurrence of extreme hydroclimatic events is also projected to increase in the future, with the probability of occurrence of droughts, such as the recent 2016 event with the lowest freshwater input in the last 70 years, doubling with respect to the historical records.Climatic Change0165-0009 Reuters ISIclimate models, digital storage, remote sensing, rivers, stream flow, water, general circulation model, historical records, hydrological modeling, index of agreements, meteorological data, oceanographic conditions, probability of occurrence, streamflow records, climate change, climate change, coastal zone, fjord, freshwater input, hydrological modeling, hydrometeorology, satellite sensor, streamflow, patagonia, puelo river
Early arboreal colonization, postglacial resilience of deciduous Nothofagus forests, and the Southern Westerly Wind influence in central-east Andean PatagoniaMoreno, P.I.; Simi, E.; Villa-Martínez, R.P.; Vilanova, I.Agua y Extremos2019.010.1016/j.quascirev.2019.06.004The history and dynamics of deciduous Nothofagus forests along the eastern slopes of the central Patagonian Andes (44°-49°S) remain insufficiently studied and understood, particularly at timescales ranging from centuries to millennia. Available fossil pollen records point to time-transgressive responses of the arboreal vegetation to climatic changes during the Last Glacial Termination (T1) and early Holocene, and spatial heterogeneity since then along north-south, east-west, and elevation transects. The degree to which these results represent biogeographic and climatic trends, varying environmental gradients, or site-specific phenomena has not been assessed in detail. Here we present a fossil pollen and macroscopic charcoal record from Lago Churrasco (45°41′S, 71°49′W), a small closed-basin lake located in the deciduous Nothofagus forest zone of the central-east Andes of Chilean Patagonia. Our results suggest that Nothofagus trees colonized newly deglaciated terrains at ∼16,000 cal yr BP and formed scrublands/woodlands several millennia earlier than reported by previous studies east of the Andes. This suggests expansion and local densification of tree populations sourced from the eastern margin of the Patagonian Ice Sheet during the Last Glacial Maximum, with the additional implication that temperature and precipitation conditions favorable for tree survival and reproduction developed early during T1. We posit that the amount of moisture delivered by the Southern Westerly Winds was not a limiting factor for arboreal expansion during T1 in this sector of the central Patagonian Andes. Closed-canopy Nothofagus forests established at ∼10,000 cal yr BP and have remained essentially invariant despite climate change and natural disturbance regimes. This resilience was challenged and exceeded by human disturbance during the 20th century through the use of fire, leading to deforestation and spread of invasive exotic species in an extraordinarily rapid event. Our record suggests a permanent influence of the Southern Westerly Winds over the last 10,000 years, with relatively modest variations at centennial and millennial timescales.Quaternary Science Reviews0277-3791 Reuters ISIcharcoal, deforestation, expansion, glacial geology, environmental gradient, invasive exotic species, last glacial maximum, last glacial terminations, natural disturbance regime, nothofagus forests, southern westerly winds, spatial heterogeneity, climate change, biogeography, climate change, climate variation, colonization, deciduous forest, deforestation, deglaciation, disturbance, fossil record, heterogeneity, last glacial maximum, limiting factor, pollen, postglacial, precipitation (climatology), reproduction, vegetation type, andes, patagonia, nothofagus
The Impacts of Native Forests and Forest Plantation on Water Supply in ChileAlvarez-Garreton, Camila; Lara, Antonio; Boisier, Juan Pablo; Galleguillos, MauricioCambio de Uso de Suelo; Agua y Extremos2019.010.3390/f10060473Over the past 40 years, south-central Chile has experienced important land-use-induced land cover changes, with massive conversion from native forests (NF) to Pinus radiata D.Don and Eucalyptus spp. exotic forest plantations (FP). Several case studies have related this conversion to a reduction in water supply within small catchments (<100 ha). In this work, we explore the impacts of NF and FP on streamflow by using a large-sample catchment dataset recently developed for Chile. We select 25 large forested catchments (>20,000 ha) in south-central Chile (35° S–41° S), analyze their land cover and precipitation spatial distributions, and fit a regression model to quantify the influence of NF, FP, grassland (GRA) and shrubland (SHR) partitions on annual runoff. To assess potential effects of land cover changes on water supply, we use the fitted model (R2 = 0.84) in synthetic experiments where NF, GRA and SHR covers within the catchments are replaced by patches of FP. We show that annual runoff consistently decreases with increments of FP, although the magnitude of the change (ranging from 2.2% to 7.2% mean annual runoff decrease for 10,000 ha increment in FP) depends on several factors, including the initial land cover partition within the basin, the replaced land cover class, the area of the catchment, and the type of catchment (drier or humid). Finally, in the context of the mitigation strategies pledged in the Chilean NDC (Nationally Determined Contributions defined after the Paris Agreement), which include the afforestation of 100,000 ha (mainly native forest) by 2030, we quantify the impacts on water supply due to the afforestation of 100,000 ha with different combinations of NF and FP. We show that annual runoff is highly sensitive to the relative area of FP to NF: ratios of FP to NF areas of 10%, 50% and 90% would lead to 3%, −18% and −40% changes in mean annual runoff, respectively. Our results can be used in the discussion of public policies and decision-making involving forests and land cover changes, as they provide scientifically-based tools to quantify expected impacts on water resources. In particular, this knowledge is relevant for decision making regarding mitigation strategies pledged in the Chilean NDC.Forests1999-4907 Reuters ISIcatchments, decision making, land use, large dataset, reforestation, regression analysis, runoff, chile, forest plantation, grassland, land use and land cover change, native forests, shrublands, water provision, water supply, grassland, land cover, land use change, plantation forestry, runoff, shrubland, streamflow, water supply, chile, decision making, land use, reforestation, regression analysis, runoff, chile, eucalyptus, pinus radiata
Anthropogenic drying in central-southern Chile evidenced by long-term observations and climate model simulationsBoisier, Juan P.; Alvarez-Garretón, Camila; Cordero, Raúl R.; Damiani, Alessandro; Gallardo, Laura; Garreaud, René D.; Lambert, Fabrice; Ramallo, Cinthya; Rojas, Maisa; Rondanelli, RobertoCiudades Resilientes; Zonas Costeras; Agua y Extremos; Gobernanza e Interfaz Ciencia y Política2018.010.1525/elementa.328The socio-ecological sensitivity to water deficits makes Chile highly vulnerable to global change. New evidence of a multi-decadal drying trend and the impacts of a persistent drought that since 2010 has affected several regions of the country, reinforce the need for clear diagnoses of the hydro-climate changes in Chile. Based on the analysis of long-term records (50+ years) of precipitation and streamflow, we confirm a tendency toward a dryer condition in central-southern Chile (30–48°S). We describe the geographical and seasonal character of this trend, as well as the associated large-scale circulation pat- terns. When a large ensemble of climate model simulations is contrasted to observations, anthropogenic forcing appears as the leading factor of precipitation change. In addition to a drying trend driven by greenhouse gas forcing in all seasons, our results indicate that the Antarctic stratospheric ozone deple- tion has played a major role in the summer rainfall decline. Although average model results agree well with the drying trend’s seasonal character, the observed change magnitude is two to three times larger than that simulated, indicating a potential underestimation of future projections for this region. Under present-day carbon emission rates, the drying pathway in Chile will likely prevail during the next decades, although the summer signal should weaken as a result of the gradual ozone layer recovery. The trends and scenarios shown here pose substantial stress on Chilean society and its institutions, and call for urgent action regarding adaptation measures.Elementa: Science of the Anthropocene2325-1026 Reuters ISIanthropogenic effect, carbon emission, climate modeling, drought, greenhouse gas, long-term change, ozone depletion, simulation, streamflow, trend analysis, vulnerability, chile
Anthropocene and streamflow: Long-term perspective of streamflow variability and water rightsBarria, Pilar; Rojas, Maisa; Moraga, Pilar; Muñoz, Ariel; Bozkurt, Deniz; Alvarez, CamilaAgua y Extremos; Gobernanza e Interfaz Ciencia y Política; Transversal2019.010.1525/elementa.340Since 1981, water allocation in Chile has been based on a water use rights (WURs) market, with limited regulatory and supervisory mechanisms. The volume to be granted as permanent and eventual WURs is calculated from streamflow records, if stream gauge data are available, or from hydrologic parameter transfer from gauged to ungauged catchments, usually with less than 50 years of record. To test the per- formance of this allocation system, while analyzing the long-term natural variability in water resources, we investigated a 400 year-long (1590–2015) tree-ring reconstruction of runoff and historical water rights for Perquilauquén at Quella catchment, a tributary to the Maule River in Central Chile (35°S–36°30S). Furthermore, we assess how the current legislation would perform under a projected climate scenario, based on historical climate simulations of runoff calibrated against observed data, and future projections. Our analyses indicate that the allocation methodology currently applied by the Water Authority in Chile is very sensitive to the time window of data used, which leads to an underestimation of variability and long-term trends. According to the WURs database provided by the Chilean Water Directorate, WURs at Perquilauquén at Quella are already over-allocated. Considering regional climate projections, this condition will be exacerbated in the future. Furthermore, serious problems regarding the access and quality of infor- mation on already-granted WURs and actual water usage have been diagnosed, which further encumber environmental strategies to deal with and adapt to climate change. We emphasize the urgent need for a review and revision of current water allocation methodologies and water law in Chile, which are not concordant with the dynamics and non-stationarity of hydrological processes. Water scarcity and water governance are two of the key issues to be faced by Chile in the Anthropocene.Elementa: Science of the Anthropocene2325-1026 Reuters ISIanthropocene, catchment, database, human rights, hydrological regime, planning legislation, regional climate, regulatory framework, streamflow, tributary, water resource, water use efficiency, chile, maule, maule river
Strongest MJO on Record Triggers Extreme Atacama Rainfall and Warmth in AntarcticaRondanelli, R.; Hatchett, B.; Rutllant, J.; Bozkurt, D.; Garreaud, R.Zonas Costeras; Agua y Extremos; Transversal2019.010.1029/2018GL081475Tropical perturbations have been shown theoretically and observationally to excite long range atmospheric responses in the form of Rossby wave teleconnections that result from the equator to pole gradient of planetary vorticity. An extreme teleconnection event occurred during March 2015 in the Southeastern Pacific. As a result, extreme high temperatures were observed in Southwestern South America and the Antarctic Peninsula simultaneously with an extreme rainfall and flood event in the hyperarid Atacama desert.%%%%%%We show that the origin of these seemingly disconnected extreme events can be traced to a Rossby wave response to the strongest Madden‐Julian Oscillation (MJO) on record in the tropical central Pacific. A barotropic wavenumber 3 to 4 perturbation with group velocity between 15 to 30 m/s is consistent with the trajectory and timing followed by the upper level anomalies radiating away from the tropics after the MJO episode.Geophysical Research Letters0094-8276 Reuters ISIflood control, floods, mechanical waves, oil well flooding, rain, tropics, antarctic peninsula, antarctica, atmospheric response, climate dynamics, extremes, madden-julian oscillation, rossby wave, rossby wave response, climatology, air-sea interaction, barotropic wave, climate change, extreme event, flood, flooding, high temperature, madden-julian oscillation, rainfall, rossby wave, teleconnection, wave velocity, antarctic peninsula, antarctica, atacama desert, chile, pacific ocean, pacific ocean (central), pacific ocean (southeast), south america, west antarctica
Centennial‐Scale SE Pacific Sea Surface Temperature Variability Over the Past 2,300 YearsCollins, James A.; Lamy, Frank; Kaiser, Jérôme; Ruggieri, Nicoletta; Henkel, Susann; De Pol‐Holz, Ricardo; Garreaud, René; Arz, Helge W.Cambio de Uso de Suelo; Agua y Extremos2019.010.1029/2018PA003465Detailed temperature reconstructions over the past 2,000 years are important for contextualizing modern climate change. The midlatitude SE Pacific is a key region in this regard in terms of understanding the climatic linkages between the tropics and southern high latitudes. Multicentennial timescale temperature variability remains, however, poorly understood, due to a lack of long, high-temporal-resolution temperature records from this region and from the southern high latitudes in general. We present a unique alkenone sea surface temperature (SST) record from 44°S on the southern Chilean margin in the SE Pacific spanning the last 2,300 years at decadal resolution. The record displays relatively large changes including a cooling transition from 14 to 12.5 °C between 1,100 and 600 cal yr BP, in line with other Chile margin SST records and coeval with Antarctic cooling. This cooling is attributable to reduced Southern Ocean deep convection, driven by a late Holocene sea-ice increase in the Weddell Sea associated with increased El-Niño Southern Oscillation variability. Superimposed on the late Holocene cooling, we observe multicentennial timescale SST variability, including relatively cool SSTs (12.5 °C) from 950 to 500 cal yr BP, corresponding to the Medieval Climate Anomaly, and warmer SSTs (13 °C) from 500 to 200 cal yr BP, corresponding to the Little Ice Age. These oscillations may reflect either multicentennial internal variability of the Southern Ocean deep convection and/or multicentennial variability in the phasing of El-Niño Southern Oscillation and Southern Annular Mode events. ©2019. American Geophysical Union. All Rights Reserved.Paleoceanography and Paleoclimatology2572-4517 Reuters ISIclimate change, convection, cooling, el nino-southern oscillation, holocene, medieval warm period, reconstruction, sea ice, sea surface temperature, pacific ocean, pacific ocean (southeast), southern ocean, weddell sea
GIMMS NDVI time series reveal the extent, duration, and intensity of “blooming desert” events in the hyper-arid Atacama Desert, Northern ChileChávez, R.O.; Moreira-Muñoz, A.; Galleguillos, M.; Olea, M.; Aguayo, J.; Latín, A.; Aguilera-Betti, I.; Muñoz, A.A.; Manríquez, H.Cambio de Uso de Suelo; Agua y Extremos2019.010.1016/j.jag.2018.11.013The “blooming desert”, or the explosive development and flowering of ephemeral herbaceous and some woody desert species during years with abnormally high accumulated rainfall, is a spectacular biological phenomenon of the hyper-arid Atacama Desert (northern Chile) attracting botanists, ecologists, geo-scientists, and the general public from all over the world. However, the number of “blooming deserts”, their geographical distribution and spatio-temporal patterns have not been quantitatively assessed to date. Here, we used NDVI data from the Global Inventory Modeling and Mapping Studies (GIMMS) project to reconstruct the annual land surface phenology (LSP) of the Atacama Desert using a non-parametric statistical approach. From the reconstructed LSP, we detected the “blooming deserts” as positive NDVI anomalies and assessed three dimensions of the events: their temporal extent, intensity of “greening” and spatial extent. We identified 13 “blooming deserts” between 1981 and 2015, of which three (1997–98, 2002–03, and 2011) can be considered major events according to these metrics. The main event occurred in 2011, spanning 180 days between July and December 2011, and spread over 11,136 km 2 of Atacama dry plains. “Blooming deserts” in Atacama have been triggered by the accumulation of precipitation during a period of 2 to 12 months before and during the events. The proposed three-dimensional approach allowed us to characterize different types of “blooming deserts”: with longer episodes or larger spatial distribution or with different “greening” intensities. Its flexibility to reconstruct different LSP and detect anomalies makes this method a useful tool to study these rare phenomena in other deserts in the world also.International Journal of Applied Earth Observation and Geoinformation0303-2434 Reuters ISIdesert, extreme event, land surface, numerical model, phenology, precipitation intensity, remote sensing, time series, vegetation mapping, atacama desert, chile
Geohistorical records of the Anthropocene in ChileGayo, E. M.; McRostie, V.; Campbell, R.; Flores, C.; Maldonado, A.; Uribe-Rodriguez, M.; Moreno, P. I.; Santoro, C.; Christie, D. A.; Muñoz, A. A.; Gallardo, L.Ciudades Resilientes; Agua y Extremos10.1525/elementa.353The deep-time dynamics of coupled socio-ecological systems at different spatial scales is viewed as a key framework to understand trends and mechanisms that have led to the Anthropocene. By integrating archeological and paleoenvironmental records, we test the hypothesis that Chilean societies progressively escalated their capacity to shape national biophysical systems as socio-cultural complexity and pressures on natural resources increased over the last three millennia. We demonstrate that Pre-Columbian societies intentionally transformed Chile’s northern and central regions by continuously adjusting socio-cultural practices and/or incorporating technologies that guaranteed resource access and social wealth. The fact that past human activities led to cumulative impacts on diverse biophysical processes, not only contradicts the notion of pristine pre-Industrial Revolution landscapes, but suggests that the Anthropocene derives from long-term processes that have operated uninterruptedly since Pre-Columbian times. Moreover, our synthesis suggests that most of present-day symptoms that describe the Anthropocene are rooted in pre-Columbian processes that scaled up in intensity over the last 3000 years, accelerating after the Spanish colonization and, more intensely, in recent decades. The most striking trend is the observed coevolution between the intensity of metallurgy and heavy-metal anthropogenic emissions. This entails that the Anthropocene cannot be viewed as a universal imprint of human actions that has arisen as an exclusive consequence of modern industrial societies. In the Chilean case, this phenomenon is intrinsically tied to historically and geographically diverse configurations in society-environment feedback relationships. Taken collectively with other case studies, the patterns revealed here could contribute to the discussion about how the Anthropocene is defined globally, in terms of chronology, stratigraphic markers and attributes. Furthermore, this deep-time narrative can potentially become a science-based instrument to shape better-informed discourses about the socio-environmental history in Chile. More importantly, however, this research provides crucial “baselines” to delineate safe operating spaces for future socio-ecological systems.Elem Sci Anth2325-1026 Reuters ISIanthropocene, anthropogenic source, archaeology, biophysics, coevolution, colonization, complexity, heavy metal, historical record, landscape, metallurgy, paleoenvironment, social change
Dynamical downscaling over the complex terrain of southwest South America: present climate conditions and added value analysisBozkurt, Deniz; Rojas, Maisa; Boisier, Juan Pablo; Rondanelli, Roberto; Garreaud, René; Gallardo, LauraCiudades Resilientes; Zonas Costeras; Agua y Extremos; Gobernanza e Interfaz Ciencia y Política; Transversal2019.010.1007/s00382-019-04959-yThis study evaluates hindcast simulations performed with a regional climate model (RCM, RegCM4) driven by reanalysis data (ERA-Interim) over the Pacific coast and Andes Cordillera of extratropical South America. A nested domain configuration at \(0.44^{\circ }\) ( \(\sim\) 50 km) and \(0.09^{\circ }\) ( \(\sim\) 10 km) spatial resolutions is used for the simulations. RegCM4 is also driven by a global climate model (GCM, MPI-ESM-MR) on the same domain configuration to asses the added values for temperature and precipitation (historical simulations). Overall, both 10 km hindcast and historical simulation results are promising and exhibit a better representation of near-surface air temperature and precipitation variability compared to the 50 km simulations. High-resolution simulations suppress an overestimation of precipitation over the Andes Cordillera of northern Chile found with the 50 km simulations. The simulated daily temperature and precipitation extreme indices from 10 km hindcast simulation show a closer estimation of the observed fields. A persistent warm bias ( \(\sim +\,{4\,}^{\circ }\hbox {C}\) ) over the Atacama Desert in 10 km hindcast simulation reveals the complexity in representing land surface and radiative processes over the desert. Difficulties in capturing the temperature trend in northern Chile are notable for both hindcast simulations. Both resolutions exhibit added values for temperature and precipitation over large parts of Chile, in particular, the 10 km resolves the coastal-valley Andes transitions over central Chile. Our results highlight that resolutions coarser than 50 km (e.g., GCMs and reanalysis) miss important climate gradients imposed by complex topography. Given that the highest spatial resolution of the current regional simulations over the South America is about 50 km, higher resolutions are important to improve our understanding of the dynamical processes that determine climate over complex terrain and extreme environments.Climate Dynamics0930-7575 Reuters ISIclimate conditions, climate modeling, climate variation, complex terrain, downscaling, regional climate, spatial analysis, temporal analysis, andes, atacama desert, chile, patagonia, equus asinus
2018 International Atmospheric Rivers Conference: Multi‐disciplinary studies and high‐impact applications of atmospheric riversRamos, Alexandre M.; Wilson, Anna M.; DeFlorio, Michael J.; Warner, Michael D.; Barnes, Elizabeth; Garreaud, Rene; Gorodetskaya, Irina V.; Lavers, David A.; Moore, Benjamin; Payne, Ashley; Smallcomb, Chris; Sodemann, Harald; Wehner, Michael; Ralph, Fred MartinAgua y Extremos2019.010.1002/asl.935Atmospheric rivers (ARs) play a vital role in shaping the hydroclimate of many regions globally, and can substantially impact water resource management, emergency response planning, and other socioeconomic entities. The second International Atmospheric Rivers Conference took place at the Scripps Institution of Oceanography, University of California, San Diego, during 25–28 June, 2018, in La Jolla, California, USA. It was sponsored by the Center for Western Weather and Water Extremes (CW3E). A total of 120 people attended the Conference with 94 abstracts submitted and 30 participating students. In addition to the conference, the Student Forecasting Workshop was organised in the same week. During this workshop, students were exposed to AR forecasting tools, and learned examples of how these tools could be used to make decisions for various applications. The main goals of this conference were to bring together experts from across the fields of hydrology, atmospheric, oceanic, and polar sciences, as well as water management, civil engineering, and ecology to advance the state of AR science and to explore the future directions for the field. The conference was organised into traditional oral and poster presentations, along with panel discussions and Breakout Groups. This format allowed enhanced interaction between participants, driving progress within the scientific community and the enhanced communication of societal needs by various stakeholders. Several emerging topics of research were highlighted, including subseasonal‐to‐seasonal (S2S) prediction of ARs and an overview of the AR Reconnaissance campaign. In addition to providing a forum to disseminate and debate new results from scientific talks and posters, the conference was equally effective and useful in linking scientists to users and decision‐makers that require improved knowledge on ARs to manage resources and prepare for hazards. The third International Atmospheric Rivers Conference will be held in Chile in 2020, and hosted by the University of Chile, Santiago.Atmospheric Science Letters1530-261X Reuters ISIatmosphere, conference proceeding, knowledge, research work, student, california, chile, la jolla, metropolitana, san diego, united states
The Role of Streamside Native Forests on Dissolved Organic Matter in Forested and Agricultural Watersheds in Northwestern PatagoniaBecerra-Rodas, Constanza; Little, Christian; Lara, Antonio; Sandoval, Jorge; Osorio, Sebastián; Nimptsch, JorgeCambio de Uso de Suelo; Agua y Extremos2019.010.3390/f10070595Streamside native forests are known for their key role in water provision, commonly referred to as buffers that control the input or output of nutrients from terrestrial to aquatic ecosystems (i.e., nitrogen or carbon cycle). In order to assess the functional role of indigenous forests along streamside channels, we measured 10 parameters associated with DOM (Dissolved Organic Matter) at 42 points in 12 small catchments (15–200 ha) dominated by native forests (reference, WNF), forest plantations (WFP) and agricultural lands (WAL) in which the land cover portion was calculated in the entire watershed and along 30 and 60-m wide buffer strips. We found that watersheds WFP and WAL were statistically different than WNF, according to DIC concentrations (Dissolved Inorganic Carbon) and the intensity of the maximum fluorescence of DOM components. Using linear models, we related streamside native forest coverage in buffer strips with DOM parameters. The increase of streamside native forest coverage in 60 m wide buffer strips (0–100%) was related to lower DIC concentrations (0.89 to 0.28 mg C L−1). In watersheds WFP and WAL, the humic and fulvic-like components (0.42 to 1.42 R.U./mg C L−1) that predominated were related to an increase in streamside native forest coverage in the form of a 60 m wide buffer strip (0–75%). This is evidence that streamside native forests influence outputs of detritus and lowered in-stream processing with concomitant downstream transport, and functional integrity and water quality. We propose that DOM quantity and quality may be a potential tool for the identification of priority areas near streams for conservation and ecological restoration in terms of recovery of water quality as an important ecosystem service. The results of this study are useful to inform policy and regulations about the width of streamside native forests as well as their characteristics and restrictions.Forests1999-4907 Reuters ISIaquatic ecosystems, biogeochemistry, biological materials, carbon, dissolution, organic compounds, runoff, water quality, watersheds, agricultural land, catchment management, dissolved organic matters, forest plantation, native forests, riparian vegetation, streamside native buffer, forestry, agricultural land, buffer zone, catchment, conservation management, dissolved organic carbon, ecosystem service, plantation forestry, restoration ecology, riparian vegetation, water quality, watershed, carbon, dissolving, forestry, organic compounds, runoff, water quality, patagonia
Extreme Daily Rainfall in Central-Southern Chile and Its Relationship with Low-Level Horizontal Water Vapor FluxesValenzuela, Raúl A.; Garreaud, René D.Agua y Extremos2019.010.1175/JHM-D-19-0036.1Extreme rainfall events are thought to be one of the major threats of climate change given an increase of water vapor available in the atmosphere. However, before projecting future changes in extreme rainfall events, it is mandatory to know current patterns. In this study we explore extreme daily rainfall events along central-southern Chile with emphasis in their spatial distribution and concurrent synoptic-scale circulation. Surface rain gauges and reanalysis products from the Climate Forecast System Reanalysis are employed to unravel the dependency between extreme rainfall and horizontal water vapor fluxes. Results indicate that extreme rainfall events can occur everywhere, from the subtropical to extratropical latitudes, but their frequency increases where terrain has higher altitude, especially over the Andes Mountains. The majority of these events concentrate in austral winter, last a single day, and encompass a north–south band of about 200 km in length. Composited synoptic analyses identified extreme rainfall cases dominated by northwesterly (NW) and westerly (W) moisture fluxes. Some features of the NW group include a 300-hPa trough projecting from the extratropics to subtropics, a surface-level depression, and cyclonic winds at 850 hPa along the coast associated with integrated water vapor (IWV) > 30 mm. Conversely, features in the W group include both a very weak 300-hPa trough and surface depression, as well as coastal westerly winds associated with IWV > 30 mm. About half of extreme daily rainfall is associated with an atmospheric river. Extreme rainfall observed in W (NW) cases has a strong orographic (synoptic) forcing. In addition, W cases are, on average, warmer than NW cases, leading to an amplified hydrological response.Journal of Hydrometeorology1525-755X Reuters ISIdiurnal variation, extreme event, precipitation assessment, precipitation intensity, raingauge, spatiotemporal analysis, water flux, water vapor, chile
The last glacial termination in the Coyhaique sector of central PatagoniaVilanova, I.; Moreno, P.I.; Miranda, C.G.; Villa-Martínez, R.P.Agua y Extremos2019.010.1016/j.quascirev.2019.105976Quaternary Science Reviews0277-3791 Reuters ISIglacial geology, lakes, reforestation, vegetation, biological productivity, continental landmass, deep water convection, glacial terminations, last glacial maximum, last glacial terminations, southern south america, southern westerly winds, climate change, climate change, glacial-interglacial cycle, global climate, ice-dammed lake, last glacial, last glacial maximum, precipitation (climatology), proglacial environment, treeline, upwelling, westerly, aisen, andes, chile, coihaique, patagonia, southern ocean
Growth and steady state of the Patagonian AndesColwyn, David Auerbach; Brandon, Mark T.; Hren, Michael T.; Hourigan, Jeremy; Pacini, Astrid; Cosgrove, Martha G.; Midzik, Maya; Garreaud, René D.; Metzger, ChristineAgua y Extremos2019.010.2475/06.2019.01Water isotopes are an important tool for reconstructing the amount of atmospheric lifting related to high topography in the geologic past. However, our capacity for meaningful interpretation requires understanding the climatic setting and isolating the influence of orography on water isotopes. Patagonia’s simple, steady climatology and location within the Southern Westerlies makes it an ideal setting for successful application of water isotopes to measuring topography through time. Here we use hydrated volcanic glass to construct a new record of the size of the Patagonian Andes during the Cenozoic. We also utilize a novel method for identifying the contribution of orography in regional climate records. Our results show that variation in the observed record can largely be explained by variations in climate. Thus we conclude that the mountain range has maintained a size similar to modern since at least Paleocene. This result is in agreement with geologic data, which constrain the bulk of the surface uplift of the Andes to the Cretaceous. The reconstruction of the Patagonian Andes, which grew in the Cretaceous and remained high through the Cenozoic, is markedly different from the widely held view of Miocene formation of this mountain range. In particular, the topography appears to remain stable during the northward propagation and collision of offshore spreading centers.American Journal of Science0002-9599 Reuters ISIcenozoic, climate variation, collision zone, cretaceous, growth rate, isotopic composition, orographic effect, paleoatmosphere, paleocene, paleoclimate, paleotopography, reconstruction, regional climate, spreading center, volcanic glass, water chemistry, patagonia
A 15,400-year long record of vegetation, fire-regime, and climate changes from the northern Patagonian AndesJara, Ignacio A.; Moreno, Patricio I.; Alloway, Brent V.; Newnham, Rewi M.Agua y Extremos2019.010.1016/j.quascirev.2019.106005Paleoecological studies from the northern Patagonian Andes (40–44°S) have identified past changes in vegetation, fire regimes and paleoclimate since the last glaciation, including variations in strength and position of the Southern Westerly Winds (SWW). The extent to which records west and east of the Andes provide a congruent paleoclimatic history, however, has not been explored in detail in the literature. Physical and biological contrasts are evident between these regions today and are to be expected in paleoclimate reconstructions. In this context, we present pollen and charcoal records from sediment cores collected in Lago Espejo, a small closed-basin lake located in the core sector of the northern Patagonian Andes that spans uninterrupted the last ∼15,400 years. Following glacier withdrawal, the vegetation surrounding Lago Espejo features scattered Nothofagus woodlands, including relatively thermophilous rainforest trees between ∼15,400 and 14,400 cal yr BP. The disappearance of these trees and an abrupt rise in Nothofagus at ∼14,400 cal yr BP mark the establishment of closed-canopy forests during the Antarctic Cold Reversal, followed by increases in the cold-tolerant hygrophilous conifer Podocarpus nubigena during the Younger Dryas (∼12,700–11,500 cal yr BP). The Holocene vegetation consists of Nothofagus-dominated forests with modest variation in composition and structure until the present, attesting to the resilience of these forest communities to climate change and natural disturbance regimes. Rapid deforestation, anthropogenic fires and the establishment of artificial meadows with exotic herbs introduced by Europeans at ∼150 cal yr BP, triggered a rapid, large-magnitude landscape transformation unprecedented in the last 14,000 years. The timing and structure of vegetation changes revealed by the Lago Espejo record suggest that changes in the SWW were the main driver of vegetation and fire regimes in the Andes of northern Patagonia over the last 15,400 years. Comparison between multiple reconstructions from northern Patagonia reveals overall coherent vegetation and fire regime changes in the western and Andean sectors, and a spatially variable and more divergent behaviour in sites located further east. This spatial patter is akin to the present-day correlation between precipitation and SWW in this region.Quaternary Science Reviews0277-3791 Reuters ISIcharcoal, deforestation, fires, glacial geology, repair, vegetation, disturbance regime, northern patagonia, nothofagus forests, southern andes, southern westerly winds, climate change, climate change, coniferous tree, fire history, holocene, hydrological regime, paleoclimate, palynology, rainforest, westerly, younger dryas, andes, patagonia, coniferophyta, nothofagus, podocarpus nubigenus
Bias correction of global high-resolution precipitation climatologies using streamflow observations from 9372 catchmentsBeck, Hylke E.; Wood, Eric F.; McVicar, Tim R.; Zambrano-Bigiarini, Mauricio; Alvarez-Garreton, Camila; Baez-Villanueva, Oscar M.; Sheffield, Justin; Karger, Dirk N.Agua y Extremos2019.010.1175/JCLI-D-19-0332.1We introduce a set of global high-resolution (0.05 ◦ ) precipitation ( P) climatologies corrected for bias using streamflow ( Q) observations from 9372 stations worldwide. For each station, we inferred the “true” long-term P using a Budyko curve, an empirical equation relating long-term P, Q, and potential evaporation. We subsequently calculated long-term bias correction factors for three state-of-the-art P climatologies (WorldClim V2, CHELSA V1.2, and CHPclim V1), after which we used random forest regression to produce global gap-free bias correction maps for the climatologies. Monthly climatological bias correction factors were calculated by disaggregating the long-term bias correction factors based on gauge catch efficiencies. We found that all three climatologies systematically underestimate P over parts of all major mountain ranges globally, despite the explicit consideration of orography in the production of each climatology. Additionally, all climatologies underestimate P at latitudes > 60 ◦ N, likely due to gauge under-catch. Exceptionally high long-term correction factors ( > 1 .5) were obtained for all three climatologies in Alaska, High Mountain Asia, and Chile — regions characterized by marked elevation gradients, sparse gauge networks, and significant snowfall. Using the bias-corrected WorldClim V2, we demonstrated that other widely used P datasets (GPCC V2015, GPCP V2.3, and MERRA-2) severely underestimate P over Chile, the Himalayas, and along the Pacific coast of North America. Mean P for the global land surface based on the bias-corrected WorldClim V2 is 862 mm yr −1 (a 9.4 % increase over the original WorldClim V2). The annual and monthly bias-corrected P climatologies have been released as the Precipitation Bias CORrection (PBCOR) dataset — downloadable via .Journal of Climate0894-8755 Reuters ISIcatchments, decision trees, earth (planet), gages, random forests, stream flow, surface measurement, correction factors, elevation gradient, empirical equations, global land surface, mountain ranges, potential evaporation, precipitation climatology, state of the art, climatology, catchment, correlation, precipitation (climatology), rainfall-runoff modeling, raingauge, sampling bias, spatial resolution, streamflow
Validation of Cryogenic Vacuum Extraction of Pore Water from Volcanic Soils for Isotopic AnalysisRivera, Diego; Gutierrez, Karen; Valdivia-Cea, Walter; Zambrano-Bigiarini, Mauricio; Godoy-Faúndez, Alex; Álvez, Amaya; Farías, LauraZonas Costeras; Agua y Extremos2019.010.3390/w11112214Andean headwater catchments are key components of the hydrological cycle, given that they capture moisture, store water and release it for Chilean cities, industry, agriculture, and cities in Chile. However, knowledge about within-Andean catchment processes is far from clear. Most soils in the Andes derive from volcanic ash Andosols and Arenosols presenting high organic matter, high-water retention capacity and fine pores; and are very dry during summer. Despite their importance, there is little research on the hillslope hydrology of Andosols. Environmental isotopes such as Deuterium and 18-O are direct tracers for water and useful on analyzing water-soil interactions. This work explores, for the first time, the efficiency of cryogenic vacuum extraction to remove water from two contrasting soil types (Arenosols, Andosols) at five soil water retention energies (from −1500 to −33 kPa). Two experiments were carried out to analyse the impact of extraction time, and initial water content on the amount of extracted water, while a third experiment tested whether the cryogenic vacuum extraction changed the isotopic ratios after extraction. Minimum extraction times to recover over 90% of water initially in the soil samples were 40–50 min and varied with soil texture. Minimum volume for very dry soils were 0.2 mL (loamy sand) and 1 mL (loam). After extraction, the difference between the isotope standard and the isotopic values after extraction was acceptable. Thus, we recommend this procedure for soils derived from volcanic ashes.Water2073-4441 Reuters ISIcatchments, cryogenics, isotopes, runoff, soil moisture, textures, volcanoes, cryogenic vacuum, environmental isotopes, hillslope hydrology, initial water contents, isotopic analysis, soil water retention, volcanic soils, water-soil interaction, extraction, catchment, deuterium, equipment component, extraction method, hillslope, isotopic analysis, soil water potential, tracer, volcanic ash, volcanic soil, water content, water retention, water-rock interaction, andes, chile
Detecting Nothofagus pumilio Growth Reductions Induced by Past Spring Frosts at the Northern Patagonian AndesSangüesa-Barreda, Gabriel; Villalba, Ricardo; Rozas, Vicente; Christie, Duncan A.; Olano, José MiguelAgua y Extremos2019.010.3389/fpls.2019.01413Frontiers in Plant Science1664-462X Reuters ISIclimate change, dendroecology, extreme event, frost damage, temperature pattern, tree rings, warm spring
+A 5680-year tree-ring temperature record for southern South AmericaLara, A.; Villalba, R.; Urrutia-Jalabert, R.; González-Reyes, A.; Aravena, J.C.; Luckman, B.H.; Cuq, E.; Rodríguez, C.; Wolodarsky-Franke, A.Cambio de Uso de Suelo; Agua y Extremos2020.010.1016/j.quascirev.2019.106087It is widely documented that the Earth’s surface temperatures have increased in recent decades. However, temperature increment patterns are not uniform around the globe, showing different or even contrasting trends. Here we present a mean maximum summer temperature record, based on tree-ring widths, over the past 5682 years (3672BC – 2009AD) for southern South America (SSA), covering from mid-Holocene to the present. This is the longest such record for the Southern Hemisphere (SH), and expands available annual proxy climate records for this region in more than 2060 years. Our record explains 49% of the temperature variation, and documents two major warm periods between 3140–2800BC and 70BC – 150AD, which coincide with the lack of evidence of glacier advances in SSA. Recent decades in the reconstruction (1959–2009) show a warming trend that is not exceptional in the context of the last five millennia. The long-term relationship between our temperature reconstruction and a reconstructed total solar irradiance record, with coinciding cycles at 293, 372, 432–434, 512 and 746 years, indicate a persistent influence of solar forcing on centennial climate variability in SSA. At interannual to interdecadal scales, reconstructed temperature is mainly related to the internal climate variability of the Pacific Ocean, including El Niño Southern Oscillation (ENSO) and longer oscillations. Our study reveals the need to characterize regional-scale climate variability and its drivers, which in the context of global-scale processes such as anthropogenic warming, interact to modulate local climate affecting humans and ecosystems.Quaternary Science Reviews0277-3791 Reuters ISIatmospheric pressure, forestry, holocenes, internal climate variability, long-term relationships, paleoclimatology, south america, temperature reconstruction, total solar irradiance, tree rings, climatology, el nino-southern oscillation, paleoclimate, paleotemperature, proxy climate record, tree ring, trend analysis, south america
Hydrological Processes Special Issue “Hydrological processes across climatic and geomorphological gradients of Latin America”Birkel, Christian; Moore, Georgianne W.; Zambrano‐Bigiarini, MauricioAgua y Extremos2019.010.1002/hyp.13648In this special issue of Hydrological Processes, we showcase the variety of ongoing research in catchments of the hydrometeorological, geomorphological, and biogeographical megadiverse region of Latin America and the Caribbean (LAC). The papers of this special issue address hydrological processes that regulate storage, mixing, and fluxes of water and solutes from the driest Atacama Desert in Chile (annual precipitation lower than 10 mm in some places) to the wettest mountainous areas of Central America (annual rainfall up to 8,000 mm), including the richest biodiversity on Earth present in the Amazon. Not only are tropical rainforest ecosystems poorly represented in hydrologic research, the LAC contains a myriad of unique lowland to montane ecosystems across the climate gradient that also includes snow and ice processes. Opportunities to advance understanding of how vegetation and landforms redistribute moisture abound in the remote reaches of Latin America. Such modulation of the hydrological cycle by vegetation and large‐scale connecting driving forces of rainfall generating moisture transport is the topic of the contributions briefly introduced in the following section. There are three major transcending themes covered in this special issue: 1) hydrological processes across climate gradients, 2) unique ecosystems with limited hydrological research, 3) effects of land use change on hydrology.Hydrological Processes0885-6087, 1099-1085 Reuters ISI
Role of synoptic activity on projected changes in upwelling-favourable winds at the ocean’s eastern boundariesAguirre, Catalina; Rojas, Maisa; Garreaud, René D.; Rahn, David A.Zonas Costeras; Agua y Extremos; Gobernanza e Interfaz Ciencia y Política2019.010.1038/s41612-019-0101-9The climate of the ocean’s eastern boundaries is strongly influenced by subtropical anticyclones, which drive a surface wind stress that promotes coastal upwelling of nutrient-rich subsurface water that supports high primary productivity and an abundance of food resources. Understanding the projected response of upwelling-favourable winds to climate change has broad implications for coastal biogeochemistry, ecology, and fisheries. Here we use a reanalysis, an ensemble of global climate simulations, and an objective algorithm to track anticyclones to investigate the projected changes in upwelling-favourable wind events at the California, Canary, Humboldt, and Benguela coastal upwelling systems. Except for the north Pacific, we find consistent poleward shifts of mean and upper percentile daily winds over the ocean basins. We propose that extratropical, synoptic-scale migratory anticyclones that force intense coastal upwelling events—which become more frequent at higher latitudes and less frequent at lower latitudes in the future—play an important role in the projected changes in upwelling-favourable wind events in these coastal upwelling systems. These changes complement large-scale processes such as the poleward shift of the subtropical ridge (STR) and stationary subtropical highs. Hence, both extratropical and tropical processes need to be considered to fully explain projected changes at the coastal upwelling systems under anthropogenic climate change.npj Climate and Atmospheric Science2397-3722 Reuters ISIanthropogenic effect, anticyclone, climate change, climate modeling, computer simulation, ensemble forecasting, extratropical environment, marine atmosphere, numerical model, synoptic meteorology, tropical environment, weather forecasting, wind field, wind stress, angola, benguela, california, canada, canary islands, humboldt, saskatchewan, spain, united states
Streamflow variations across the Andes (18°–55°S) during the instrumental eraMasiokas, M. H.; Cara, L.; Villalba, R.; Pitte, P.; Luckman, B. H.; Toum, E.; Christie, D. A.; Le Quesne, C.; Mauget, S.Agua y Extremos2019.010.1038/s41598-019-53981-xThe rivers originating in the southern Andes (18°–55°S) support numerous ecosystems and a large number of human populations and socio-economic activities in the adjacent lowlands of Chile, Argentina and Bolivia. Here we show that ca. 75% of the total variance in the streamflow records from this extensive region can be explained by only eight spatially coherent patterns of variability. Five (three) of these Andean patterns exhibit extreme dry (wet) conditions in recent years, with strong interannual variations in northern Chile; long-term drying trends between 31° and 41°S; a transitional pattern in the central Patagonian Andes; and increasing trends in northwestern Argentina and southern Bolivia, the Fueguian Andes, and the eastern portion of the South Patagonian Icefield. Multivariate regression analyses show that large-scale indices of ENSO variability can predict 20% to 45% of annual runoff variability between 28° and 46°S. The influence of Antarctic and North Pacific indices becomes more relevant south of 43°S and in northwestern Argentina and southern Bolivia, respectively, but their overall skill as predictors of Andean streamflows is weak. The analyses provide relevant new information to improve understanding of the spatial coherence, the main temporal features, and the ocean-atmospheric forcings of surface runoff across the southern Andes.Scientific Reports2045-2322 Reuters ISIantarctica, argentina, article, bolivia, chile, human, sea, skill, surface runoff
A Multiscale Productivity Assessment of High Andean Peatlands across the Chilean Altiplano Using 31 Years of Landsat ImageryChávez, Roberto O.; Christie, Duncan A.; Olea, Matías; Anderson, Talia G.Agua y Extremos2019.010.3390/rs11242955The high Andean peatlands, locally known as “bofedales”, are a unique type of wetland distributed across the high-elevation South American Altiplano plateau. This extensive peatland network stores significant amounts of carbon, regulates local and regional hydrological cycles, supports habitats for a variety of plant and animal species, and has provided critical water and forage resources for the livestock of the indigenous Aymara communities for thousands of years. Nevertheless, little is known about the productivity dynamics of the high Andean peatlands, particularly in the drier western Altiplano region bordering the Atacama desert. Here, we provide the first digital peatland inventory and multiscale productivity assessment for the entire western Altiplano (63,705 km2) using 31 years of Landsat data (about 9000 scenes) and a non-parametric approach for estimating phenological metrics. We identified 5665 peatland units, covering an area of 510 km2, and evaluated the spatiotemporal productivity patterns at the regional, peatland polygon, and individual pixel scales. The regional assessment shows that the peatland areas and peatlands with higher productivity are concentrated towards the northern part of our study region, which is consistent with the Altiplano north–south aridity gradient. Regional patterns further reveal that the last seven years (2011–2017) have been the most productive period over the past three decades. While individual pixels show contrasting patterns of reductions and gains in local productivity during the most recent time period, most of the study area has experienced increases in annual productivity, supporting the regional results. Our novel database can be used not only to explore future research questions related to the social, biological, and hydrological influences on peatland productivity patterns, but also to provide technical support for the sustainable development of livestock practices and conservation and water management policy in the Altiplano region.Remote Sensing2072-4292 Reuters ISIforestry, pixels, productivity, research and development management, time series, water conservation, water management, atacama, bofedal, hydrological cycles, nonparametric approaches, npphen, phenology, productivity assessment, water management policy, wetlands
Large-sample hydrology: recent progress, guidelines for new datasets and grand challengesAddor, Nans; Do, Hong X.; Alvarez-Garreton, Camila; Coxon, Gemma; Fowler, Keirnan; Mendoza, Pablo A.Agua y Extremos2019.010.1080/02626667.2019.1683182Large-sample hydrology (LSH) relies on data from large sets (tens to thousands) of catchments to go beyond individual case studies and derive robust conclusions on hydrological processes and models. Numerous LSH datasets have recently been released, covering a wide range of regions and relying on increasingly diverse data sources to characterize catchment behaviour. These datasets offer novel opportunities, yet they are also limited by their lack of comparability, uncertainty estimates and characterization of human impacts. This article (i) underscores the key role of LSH datasets in hydrological studies, (ii) provides a review of currently available LSH datasets, (iii) highlights current limitations of LSH datasets and (iv) proposes guidelines and coordinated actions to overcome these limitations. These guidelines and actions aim to standardize and automatize the creation of LSH datasets worldwide, and to enhance the reproducibility and comparability of hydrological studies.Hydrological Sciences Journal0262-6667, 2150-3435 Reuters ISIcatchments, cloud computing, runoff, uncertainty analysis, data standardization, data uncertainty, human intervention, reproducibilities, streamflow records, large dataset, anthropogenic effect, automation, catchment, data management, data set, guideline, hydrological modeling, parallel computing, standardization, streamflow
Salmon farming vulnerability to climate change in southern Chile: understanding the biophysical, socioeconomic and governance linksSoto, Doris; León‐Muñoz, Jorge; Dresdner, Jorge; Luengo, Carol; Tapia, Fabián J.; Garreaud, RenéAgua y Extremos2019.010.1111/raq.12336There has been a growing interest in studying the labile C pool in order to promote the sequestration and stabilization of soil organic carbon (SOC). Although labile SOC fractions have emerged as standardized indicators because of their potential to detect early SOC trends over time, the relationships between microbial attributes and labile SOC remains poorly understood. In this study, we explored the influence of labile SOC fractions on the topsoil bacteria-archaea community across 28 sites with different land use, climate aridity, and soil types across a wide range of SOC content (0.6–12%) in central Chile. We applied Illumina sequencing to the 16S rRNA to examine shifts in the diversity and composition of these soil microbial communities. Additionally, labile SOC fractions such as the permanganate oxidizable carbon (POXC) and light fraction organic matter (LFOM), along with the soil physicochemical properties were analyzed. The results demonstrated that among all of the environmental factors tested, the pH, POXC/SOC ratio and LFOM were key drivers of microbial community structure (β-diversity). The α-diversity metrics exhibited a decreasing trend when aridity increased, and community structure was found to vary, with high POXC/SOC in sites associated with drier conditions. In addition, POXC/SOC ratios and LFOM were clearly related to shifts in the relative abundances of specific taxonomic groups at genera level. When there was high POXC/SOC and low LFOM content, members of Bacteroidetes (Adhaeribacter, Flavisolibacter, and Niastella), Proteobacteria (Skermanella, Ramlibacter, and Sphingomonas), and Archaea (Thaumarchaeota) were found to be the most dominant groups; however, the microbial taxa responded differently to both labile C fraction types. These results have implications for understanding how labile C content can potentially be used to predict shifts in the microbial community, thus facilitating the development of predictive ecosystem models, as well as early warning indicators for soil degradation.Reviews in Aquaculture1753-5123, 1753-5131 Reuters ISIchilean patagonia, climate change, salmon-farming employment, vulnerability
Onset and Evolution of Southern Annular Mode-Like Changes at Centennial TimescaleMoreno, P. I.; Vilanova, I.; Villa-Martínez, R.; Dunbar, R. B.; Mucciarone, D. A.; Kaplan, M. R.; Garreaud, R. D.; Rojas, M.; Moy, C. M.; De Pol-Holz, R.; Lambert, F.Cambio de Uso de Suelo; Ciudades Resilientes; Agua y Extremos; Gobernanza e Interfaz Ciencia y Política2018.010.1038/s41598-018-21836-6The Southern Westerly Winds (SWW) are the surface expression of geostrophic winds that encircle the southern mid-latitudes. In conjunction with the Southern Ocean, they establish a coupled system that not only controls climate in the southern third of the world, but is also closely connected to the position of the Intertropical Convergence Zone and CO2 degassing from the deep ocean. Paradoxically, little is known about their behavior since the last ice age and relationships with mid-latitude glacier history and tropical climate variability. Here we present a lake sediment record from Chilean Patagonia (51°S) that reveals fluctuations of the low-level SWW at mid-latitudes, including strong westerlies during the Antarctic Cold Reversal, anomalously low intensity during the early Holocene, which was unfavorable for glacier growth, and strong SWW since ∼7.5 ka. We detect nine positive Southern Annular Mode-like events at centennial timescale since ∼5.8 ka that alternate with cold/wet intervals favorable for glacier expansions (Neoglaciations) in southern Patagonia. The correspondence of key features of mid-latitude atmospheric circulation with shifts in tropical climate since ∼10 ka suggests that coherent climatic shifts in these regions have driven climate change in vast sectors of the Southern Hemisphere at centennial and millennial timescales.Scientific Reports2045-2322 Reuters ISIantarctica, article, climate change, cold stress, glaciation, holocene, lake sediment, latitude, southern hemisphere, tropic climate, writing
Record-breaking climate anomalies lead to severe drought and environmental disruption in western Patagonia in 2016Garreaud, R. D.Agua y Extremos2018.010.3354/cr01505Traditionally a temperate and hyper-humid region, western Patagonia experienced its most severe drought during the summer and fall of 2016. Along with precipitation deficits larger than 50% there was a similar reduction in river discharge into coastal waters, a decline in vegetation productivity, excessive solar radiation at the surface, and frequent upwelling-favorable wind events offshore. The combination of these regional-scale anomalies seems to have set the stage for environmental disturbances that, although not new in western Patagonia, occurred with unprecedented magnitude, including severe urban air pollution episodes, large forest fires, and the worst ever recorded harmful algae bloom (HAB). The local climate anomalies were in turn related to the concomitant strong El Niño (through atmospheric teleconnections) and, to a lesser extent, anthropogenic climate change mediated by the positive polarity of the Southern Annular Mode (SAM) and internal variability, as both modes weakened the westerlies. Dryer than present conditions are consistently projected for northern Patagonia during the 21st century as a consequence of anthropogenic increases in radiative forcing; superposition of El Niño events in this altered climate may result in a higher frequency of extreme droughts and environmental disruptions like those observed in 2016.Climate Research0936-577X Reuters ISIclimate change, environment, hab, harmful algal bloom, patagonia, sam, southern annular mode
Hydroclimatic conditions trigger record harmful algal bloom in western Patagonia (summer 2016)León-Muñoz, Jorge; Urbina, Mauricio A.; Garreaud, René; Iriarte, José LuisAgua y Extremos2018.010.1038/s41598-018-19461-4A harmful algal bloom (HAB) of the raphidophyta alga Pseudochattonella cf. verruculosa during the 2016 austral summer (February-March) killed nearly 12% of the Chilean salmon production, causing the worst mass mortality of fish and shellfish ever recorded in the coastal waters of western Patagonia. The HAB coincided with a strong El Ninõ event and the positive phase of the Southern Annular Mode that altered the atmospheric circulation in southern South America and the adjacent Pacific Ocean. This led to very dry conditions and higher than normal solar radiation reaching the surface. Using time series of atmospheric, hydrologic and oceanographic data we show here that an increase in surface water temperature and reduced freshwater input resulted in a weakening of the vertical stratification in the fjords and sounds of this region. This allowed the advection of more saline and nutrient-rich waters, ultimately resulting in an active harmful algal bloom in coastal southern Chile.Scientific Reports2045-2322 Reuters ISIalgal bloom, chile, climate, growth, development and aging, microalga, chile, climate, harmful algal bloom, microalgae
Dendrohydrology and water resources management in south-central Chile: lessons from the Río Imperial streamflow reconstructionFernández, Alfonso; Muñoz, Ariel; González-Reyes, Álvaro; Aguilera-Betti, Isabella; Toledo, Isadora; Puchi, Paulina; Sauchyn, David; Crespo, Sebastián; Frene, Cristian; Mundo, Ignacio; González, Mauro; Vignola, RaffaeleAgua y Extremos2018.010.5194/hess-22-2921-2018Streamflow in south-central Chile (SCC,  ∼  37–42° S) is vital for agriculture, forestry production, hydroelectricity, and human consumption. Recent drought episodes have generated hydrological deficits with damaging effects on these activities. This region is projected to undergo major reductions in water availability, concomitant with projected increases in water demand. However, the lack of long-term records hampers the development of accurate estimations of natural variability and trends. In order to provide more information on long-term streamflow variability and trends in SCC, here we report findings of an analysis of instrumental records and a tree-ring reconstruction of the summer streamflow of the Río Imperial ( ∼  37° 40′ S–38° 50′ S). This is the first reconstruction in Chile targeted at this season. Results from the instrumental streamflow record ( ∼  1940 onwards) indicated that the hydrological regime is fundamentally pluvial with a small snowmelt contribution during spring, and evidenced a decreasing trend, both for the summer and the full annual record. The reconstruction showed that streamflow below the average characterized the post-1980 period, with more frequent, but not more intense, drought episodes. We additionally found that the recent positive phase of the Southern Annular Mode has significantly influenced streamflow. These findings agree with previous studies, suggesting a robust regional signal and a shift to a new hydrological scenario. In this paper, we also discuss implications of these results for water managers and stakeholders; we provide rationale and examples that support the need for the incorporation of tree-ring reconstructions into water resources management.Hydrology and Earth System Sciences1607-7938 Reuters ISIdrought, forestry, stream flow, accurate estimation, forestry production, hydrological regime, hydrological scenarios, southern annular mode, streamflow variability, tree-ring reconstruction, water resources management, water resources, climate signal, dendrochronology, drought, hydrological regime, paleohydrology, reconstruction, snowmelt, streamflow, water management, water resource, chile
Foehn Event Triggered by an Atmospheric River Underlies Record-Setting Temperature Along Continental AntarcticaBozkurt, D.; Rondanelli, R.; Marín, J. C.; Garreaud, R.Zonas Costeras; Agua y Extremos; Transversal2018.010.1002/2017JD027796A record‐setting temperature of 17.5°C occurred on 24 March 2015 at the Esperanza station located near the northern tip of the Antarctic Peninsula (AP). We studied the event using surface station data, satellite imagery, reanalysis data, and numerical simulations. The Moderate Resolution Imaging Spectroradiometer Antarctic Ice Shelf Image Archive provides clear evidence for disintegration and advection of sea ice, as well as the formation of melt ponds on the ice sheet surface at the base of the AP mountain range. A deep low‐pressure center over the Amundsen‐Bellingshausen Sea and a blocking ridge over the southeast Pacific provided favorable conditions for the development of an atmospheric river with a northwest‐southeast orientation, directing warm and moist air toward the AP, and triggering a widespread foehn episode. A control simulation using a regional climate model shows the existence of local topographically induced warming along the northern tip of the AP (∼60% of the full temperature signal) and the central part of the eastern AP (>90% of the full temperature signal) with respect to a simulation without topography. These modeling results suggest that more than half of the warming experienced at Esperanza can be attributed to the foehn effect (a local process), rather than to the large‐scale advection of warm air from the midlatitudes. Nevertheless, the local foehn effect also has a large‐scale advection component, since the atmospheric river provides water vapor for orographic precipitation enhancement and latent heat release, which makes it difficult to completely disentangle the role of local versus large‐scale processes in explaining the extreme event.Journal of Geophysical Research: Atmospheres2169-897X Reuters ISIadvection, atmospheric moisture, climate change, climate modeling, extreme event, foehn, high temperature, ice shelf, meteorology, modis, regional climate, temperature, amundsen sea, antarctic peninsula, antarctica, bellingshausen sea, pacific ocean, pacific ocean (southeast), southern ocean, west antarctica, esperanza
The first 300-year streamflow reconstruction of a high-elevation river in Chile using tree rings: HIGH-ELEVATION CHILEAN RIVER STREAMFLOW RECONSTRUCTIONBarria, Pilar; Peel, Murray C.; Walsh, Kevin J. E.; Muñoz, ArielAgua y Extremos2018.010.1002/joc.5186In central Chile, increasing demand for water and decreasing runoff volumes due to drier conditions have placed catchments in this zone under water stress. However, scarcity of observed data records increases the difficulty of planning future water supply. Instrumental records suggest a reduction in streamflow over the last 56 years. However, this change is not statistically significant and the lack of meteorological stations with long records in this mountainous region hampers a deeper analysis, motivating the use of tree rings to analyse whether these changes are part of a long-term trend. This work represents the first high-elevation runoff reconstruction in Chile using 300 years of tree ring chronologies of Araucaria araucana and Astroceudrus chilensis. The upper part of Biobío river melting season runoff (October–March) and pluvial season runoff (April–September) was reconstructed and analysed to investigate the influence of large-scale climatic drivers on runoff generation, current drought trends and to improve the understanding of climate variability in this region. We obtained positive correlations between the 20-year moving average of reconstructed pluvial season runoff and reconstructed Pacific Decadal Oscillation (PDO), which is indicative of multi-decadal variability. We also found a negative correlation between the 11-year moving average of reconstructed melting season runoff and the PDO and positive correlations with the Southern Annular Mode (SAM). Important differences in the runoff variability of the upper and the lower part of the catchment were identified which are in part led by the influence of the large-scale climatic features that drive runoff generation in both regions. We found that the changes observed in the instrumental records are part of multi-decadal cycles led by the PDO and SAM for pluvial season runoff and melting season runoff, respectively.International Journal of Climatology0899-8418 Reuters ISIcatchments, climate change, digital storage, drought, forestry, melting, stream flow, water supply, decadal variability, high elevation, meteorological station, negative correlation, pacific decadal oscillation, positive correlations, southern annular mode, tree-ring chronologies, runoff, chronology, decadal variation, hydrology, reconstruction, river, runoff, streamflow, tree ring, chile, araucaria araucana
Climate variability and forest fires in central and south-central ChileUrrutia-Jalabert, Rocío; González, Mauro E.; González-Reyes, Álvaro; Lara, Antonio; Garreaud, RenéCambio de Uso de Suelo; Agua y Extremos2018.010.1002/ecs2.2171This paper evaluates the relationship between fire occurrence (number and burned area) and climate variability (precipitation and maximum temperatures) across central and south-central Chile (32°–43° S) during recent decades (1976–2013). This region sustains the largest proportion of the Chilean population, contains ecologically important remnants of endemic ecosystems, the largest extension of forest exotic plantations, and concentrates most of the fire activity in the country. Fire activity in central Chile was mainly associated with above-average precipitation during winter of the previous year and with dry conditions during spring to summer. The later association was particularly strong in the southern, wetter part of the study region. Maximum temperature had a positive significant relationship with burned area across the study region, with stronger correlations toward the south. Fires in central Chile were significantly related to El Nino~ –Southern Oscillation, through rainfall anomalies during the year previous to the fire season. The Antarctic Oscillation during winter through summer was positively related to fires across the study area due to drier/warmer conditions associated with the positive polarity of this oscillation. Climate change projections for the region reveal an all-season decrease in precipitation and increases in temperature, that may likely result in an increment of the occurrence and the area affected by fires, as it has been observed during a multi-year drought afflicting central Chile since 2010.Ecosphere2150-8925 Reuters ISIantarctic oscillation, climate change, el niño–southern oscillation (enso), exotic plantations, forest fires, mediterranean forests, temperate forests
Alternative approaches for estimating missing climate data: application to monthly precipitation records in South-Central ChileBarrios, Alonso; Trincado, Guillermo; Garreaud, RenéAgua y Extremos2018.010.1186/s40663-018-0147-xBackground Over the last decades interest has grown on how climate change impacts forest resources. However, one of the main constraints is that meteorological stations are riddled with missing climatic data. This study compared five approaches for estimating monthly precipitation records: inverse distance weighting (IDW), a modification of IDW that includes elevation differences between target and neighboring stations (IDWm), correlation coefficient weighting (CCW), multiple linear regression (MLR) and artificial neural networks (ANN). Methods A complete series of monthly precipitation records (1995–2012) from twenty meteorological stations located in central Chile were used. Two target stations were selected and their neighboring stations, located within a radius of 25 km (3 stations) and 50 km (9 stations), were identified. Cross-validation was used for evaluating the accuracy of the estimation approaches. The performance and predictive capability of the approaches were evaluated using the ratio of the root mean square error to the standard deviation of measured data (RSR), the percent bias (PBIAS), and the Nash-Sutcliffe efficiency (NSE). For testing the main and interactive effects of the radius of influence and estimation approaches, a two-level factorial design considering the target station as the blocking factor was used. Results ANN and MLR showed the best statistics for all the stations and radius of influence. However, these approaches were not significantly different with IDWm. Inclusion of elevation differences into IDW significantly improved IDWm estimates. In terms of precision, similar estimates were obtained when applying ANN, MLR or IDWm, and the radius of influence had a significant influence on their estimates, we conclude that estimates based on nine neighboring stations located within a radius of 50 km are needed for completing missing monthly precipitation data in regions with complex topography. Conclusions It is concluded that approaches based on ANN, MLR and IDWm had the best performance in two sectors located in south-central Chile with a complex topography. A radius of influence of 50 km (9 neighboring stations) is recommended for completing monthly precipitation data.Forest Ecosystems2197-5620 Reuters ISIartificial neural networks, climatological data, cross-validation, multiple linear regression
Using the Weather Research and Forecasting (WRF) Model for Precipitation Forecasting in an Andean Region with Complex TopographyYáñez-Morroni, Gonzalo; Gironás, Jorge; Caneo, Marta; Delgado, Rodrigo; Garreaud, RenéAgua y Extremos2018.010.3390/atmos9080304The Weather Research and Forecasting (WRF) model has been successfully used in weather prediction, but its ability to simulate precipitation over areas with complex topography is not optimal. Consequently, WRF has problems forecasting rainfall events over Chilean mountainous terrain and foothills, where some of the main cities are located, and where intense rainfall occurs due to cutoff lows. This work analyzes an ensemble of microphysics schemes to enhance initial forecasts made by the Chilean Weather Agency in the front range of Santiago. We first tested different vertical levels resolution, land use and land surface models, as well as meteorological forcing (GFS/FNL). The final ensemble configuration considered three microphysics schemes and lead times over three rainfall events between 2015 and 2017. Cutoff low complex meteorological characteristics impede the temporal simulation of rainfall properties. With three days of lead time, WRF properly forecasts the rainiest N-hours and temperatures during the event, although more accuracy is obtained when the rainfall is caused by a meteorological frontal system. Finally, the WSM6 microphysics option had the best performance, although further analysis using other storms and locations in the area are needed to strengthen this result.Atmosphere2073-4433 Reuters ISIland use, rain, topography, complex topographies, flash flood, land surface models, meteorological forcing, mountainous terrain, precipitation forecasting, temporal simulation, weather research and forecasting models, weather forecasting, atmospheric modeling, computer simulation, ensemble forecasting, precipitation (climatology), regional climate, temporal analysis, topography, urban atmosphere, weather forecasting
The 2010-2015 Megadrought and its influence on the fire regime in central and south-central ChileGonzález, Mauro E.; Gómez-González, Susana; Lara, Antonio; Garreaud, René; Díaz-Hormazábal, IgnacioCambio de Uso de Suelo; Agua y Extremos2018.010.1002/ecs2.2300Forest fire activity has increased in recent years in central and south-central Chile. Drought conditions have been associated with the increase of large wildfires, area burned and longer fire seasons. This study examines the influence of drought on fire regimes and discusses landscape management opportunities to decrease fire hazard. Specifically, we investigate the effect of the 2010–2015 Megadrought (MD) compared to 1990–2009 period on fire activity (fire-season length, number of fires and burned area across months, fire sizes, regions and vegetation cover types, simultaneity, and duration of fires) in central and south-central Chile (32°–39° S), using contemporary fire statistics derived from the Chilean Forest Service. For large fire events (>200 ha) the average season length increased by 67 d (44%), comparing 2010–2015 to 1990–2009. Earlier and later ignition dates resulted in extended fire seasons in MD years. During the MD, the number, area burned, simultaneity, and duration of large fires increased significantly compared to the control period, including the unprecedented occurrence of large fires during winter. The burned area in large fires increased in all vegetation types, during the MD compared to the control period, especially in the exotic plantation cover type. The regions that were most affected by fire (i.e., total area burned) during the MD wereMaule, B ıo-B ıo, and Araucan ıa (35–39° S) that concentrate >75% of forest plantations in Chile. Although both maximum temperatures and precipitation are drivers of fire activity, a simple attribution analysis indicates that the sustained rainfall deficit during 2010–2015 was the most critical factor in the enhanced fire activity. Future climate change predictions indicate more recurrent, intense, and temporally extended droughts for central and south-central Chile. Under this scenario, land-use planning and fire and forest management strategies must promote a more diverse and less flammable landscape mosaic limiting high load, homogenous, and continuous exotic plantations.Ecosphere2150-8925 Reuters ISIdrought, fire regimes, fire-prone vegetation, fire-season length
Los significados de la participación para el cambio climático en ChileSapiains Arrué, Rodolfo; Ugarte Caviedes, Ana María; Aldunce, PaulinaAgua y Extremos; Gobernanza e Interfaz Ciencia y Política2018.010.11144/Javeriana.ayd21-41.spccEste artículo analiza los distintos significados del concepto de participación, para avanzar hacia un modelo más inclusivo de gobernanza del cambio climático en Chile. Para ello, se presenta una revisión bibliográfica que discute distintas epistemologías, teorías y definiciones de la participación, con énfasis en las dificultades para su implementación en el contexto chileno. Posteriormente, se revisan los mecanismos de participación ciudadana desplegados en el desarrollo de instrumentos de gobernanza del cambio climático existentes en Chile. Se distinguen tipos de participación utilizados y se identifican experiencias conducidas desde la sociedad civil y la academia. Finalmente, se discuten los alcances y las limitaciones de los modelos de participación implementados y se resalta la importancia de incrementar la influencia de la sociedad civil y de mejorar los mecanismos existentes. Esto se explica por un escenario de cambio climático que posiblemente requerirá una mayor cantidad de actores involucrados en la toma de decisiones, para anticipar posibles divisiones frente al desarrollo de acciones de adaptación o mitigación más radicales, y que al mismo tiempo demandará mayores niveles de responsabilidad, compromiso y acción de la ciudadanía.Ambiente y Desarrollo2346-2876, 0121-7607 Reuters ISIA
Projected hydroclimate changes over Andean basins in central Chile from downscaled CMIP5 models under the low and high emission scenariosBozkurt, Deniz; Rojas, Maisa; Boisier, Juan Pablo; Valdivieso, JonásAgua y Extremos; Gobernanza e Interfaz Ciencia y Política; Transversal2018.010.1007/s10584-018-2246-7This study examines the projections of hydroclimatic regimes and extremes over Andean basins in central Chile (approximate to 30-40 degrees S) under a low and high emission scenarios (RCP2.6 and RCP8.5, respectively). A gridded daily precipitation and temperature dataset based on observations is used to drive and validate the VIC macro-scale hydrological model in the region of interest. Historical and future simulations from 19 climate models participating in CMIP5 have been adjusted with the observational dataset and then used to make hydrological projections. By the end of the century, there is a large difference between the scenarios, with projected warming of approximate to + 1.2 degrees C (RCP2.6), approximate to +3.5 degrees C (RCP8.5) and drying of approximate to - 3% (RCP2.6), approximate to - 30% (RCP8.5). Following the strong drying and warming projected in this region under the RCP8.5 scenario, the VIC model simulates decreases in annual runoff of about 40% by the end of the century. Such strong regional effect of climate change may have large implications for the water resources of this region. Even under the low emission scenario, the Andes snowpack is projected to decrease by 35-45% by mid-century. In more snowmelt-dominated areas, the projected hydrological changes under RCP8.5 go together with more loss in the snowpack (75-85%) and a temporal shift in the center timing of runoff to earlier dates (up to 5 weeks by the end of the century). The severity and frequency of extreme hydroclimatic events are also projected to increase in the future. The occurrence of extended droughts, such as the recently experienced mega-drought (2010-2015), increases from one to up to five events per 100 years under RCP8.5. Concurrently, probability density function of 3-day peak runoff indicates an increase in the frequency of flood events. The estimated return periods of 3-day peak runoff events depict more drastic changes and increase in the flood risk as higher recurrence intervals are considered by mid-century under RCP2.6 and RCP8.5, and by the end of the century under RCP8.5.Climatic Change0165-0009 Reuters ISIclimate change, drought, floods, image segmentation, probability density function, risk perception, runoff, daily precipitations, emission scenario, hydrological changes, hydrological modeling, low emission scenarios, recurrence intervals, region of interest, regional effects, climate models, air temperature, climate change, climate prediction, cmip, drought, extreme event, flood frequency, model validation, peak flow, precipitation (climatology), probability density function, runoff, scenario analysis, snowpack, andes, chile
The CAMELS-CL dataset: catchment attributes and meteorology for large sample studies – Chile datasetAlvarez-Garreton, Camila; Mendoza, Pablo A.; Boisier, Juan Pablo; Addor, Nans; Galleguillos, Mauricio; Zambrano-Bigiarini, Mauricio; Lara, Antonio; Puelma, Cristóbal; Cortes, Gonzalo; Garreaud, Rene; McPhee, James; Ayala, AlvaroCambio de Uso de Suelo; Agua y Extremos2018.010.5194/hess-22-5817-2018We introduce the first catchment dataset for large sample studies in Chile. This dataset includes 516 catchments; it covers particularly wide latitude (17.8 to 55.0°S) and elevation (0 to 6993ma.s.l.) ranges, and it relies on multiple data sources (including ground data, remote-sensed products and reanalyses) to characterise the hydroclimatic conditions and landscape of a region where in situ measurements are scarce. For each catchment, the dataset provides boundaries, daily streamflow records and basin-averaged daily time series of precipitation (from one national and three global datasets), maximum, minimum and mean temperatures, potential evapotranspiration (PET; from two datasets), and snow water equivalent. We calculated hydro-climatological indices using these time series, and leveraged diverse data sources to extract topographic, geological and land cover features. Relying on publicly available reservoirs and water rights data for the country, we estimated the degree of anthropic intervention within the catchments. To facilitate the use of this dataset and promote common standards in large sample studies, we computed most catchment attributes introduced by Addor et al. (2017) in their Catchment Attributes and MEteorology for Large-sample Studies (CAMELS) dataset, and added several others. We used the dataset presented here (named CAMELS-CL) to characterise regional variations in hydroclimatic conditions over Chile and to explore how basin behaviour is influenced by catchment attributes and water extractions. Further, CAMELS-CL enabled us to analyse biases and uncertainties in basin-wide precipitation and PET. The characterisation of catchment water balances revealed large discrepancies between precipitation products in arid regions and a systematic precipitation underestimation in headwater mountain catchments (high elevations and steep slopes) over humid regions. We evaluated PET products based on ground data and found a fairly good performance of both products in humid regions (r > 0.91) and lower correlation (r < 0.76) in hyper-arid regions. Further, the satellite-based PET showed a consistent overestimation of observation-based PET. Finally, we explored local anomalies in catchment response by analysing the relationship between hydrological signatures and an attribute characterising the level of anthropic interventions. We showed that larger anthropic interventions are correlated with lower than normal annual flows, runoff ratios, elasticity of runoff with respect to precipitation, and flashiness of runoff, especially in arid catchments. CAMELS-CL provides unprecedented information on catchments in a region largely underrepresented in large sample studies. This effort is part of an international initiative to create multi-national large sample datasets freely available for the community. CAMELS-CL can be visualised from and downloaded from and Earth System Sciences1607-7938 Reuters ISIarid regions, catchments, remote sensing, reservoirs (water), snow, time series, uncertainty analysis, catchment water balance, hydroclimatic conditions, in-situ measurement, multiple data sources, potential evapotranspiration, precipitation products, regional variation, snow water equivalent, runoff, catchment, climate conditions, data set, headwater, hydrometeorology, land cover, meteorological hazard, potential evapotranspiration, precipitation (climatology), remote sensing, runoff, streamflow, water budget, chile, camelidae
Impacts of Atmospheric Rivers on Precipitation in Southern South AmericaViale, Maximiliano; Valenzuela, Raúl; Garreaud, René D.; Ralph, F. MartinAgua y Extremos2018.010.1175/JHM-D-18-0006.1This study quantifies the impact of atmospheric rivers (ARs) on precipitation in southern South America. An AR detection algorithm was developed based on integrated water vapor transport (IVT) from 6-hourly CFSR reanalysis data over a 16-yr period (2001-16). AR landfalls were linked to precipitation using a comprehensive observing network that spanned large variations in terrain along and across the Andes from 27° to 55°S, including some sites with hourly data. Along the Pacific (west) coast, AR landfalls are most frequent between 38° and 50°S, averaging 35-40 days yr-1. This decreases rapidly to the south and north of this maximum, as well as to the east of the Andes. Landfalling ARs are more frequent in winter/spring (summer/fall) to the north (south) of ~43°S. ARs contribute 45%-60% of the annual precipitation in subtropical Chile (37°-32°S) and 40%-55% along the midlatitude west coast (37°-47°S). These values significantly exceed those in western North America, likely due to the Andes being taller. In subtropical and midlatitude regions, roughly half of all events with top-quartile precipitation rates occur under AR conditions. Median daily and hourly precipitation in ARs is 2-3 times that of other storms. The results of this study extend knowledge of the key roles of ARs on precipitation, weather, and climate in the South American region. They enable comparisons with other areas globally, provide context for specific events, and support local nowcasting and forecasting. © 2018 American Meteorological Society.Journal of Hydrometeorology1525-755X Reuters ISIatmospheric transport, extratropical cyclone, precipitation (climatology), regional climate, topographic effect, water vapor, pacific ocean, pacific ocean (south), south america
Effect of climate on tree growth in the Pampa biome of Southeastern South America: First tree-ring chronologies from UruguayLucas, Christine; Puchi, Paulina; Profumo, Ludmila; Ferreira, Alex; Muñoz, ArielAgua y Extremos2018.010.1016/j.dendro.2018.10.004Tree-ring research in the highland tropics and subtropics represents a major frontier for understanding climate-growth relationships. Nonetheless, there are many lowland regions – including the South American Pampa biome – with scarce tree ring data. We present the first two tree-ring chronologies for Scutia buxifolia in subtropical Southeastern South America (SESA), using 54 series from 29 trees in two sites in northern and southern Uruguay. We cross-dated annual rings and compared tree growth from 1950 to 2012 with regional climate variability, including rainfall, temperature and the Palmer Drought Severity Index – PDSI, the El Niño Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Overall, ring width variability was highly responsive to climate signals linked to water availability. For example, tree growth was positively correlated with accumulated rainfall in the summer-fall prior to ring formation for both chronologies. Summer climate conditions were key for tree growth, as shown by a negative effect of hot summer temperatures and a positive correlation with PDSI in late austral summer. The El Niño phase in late spring/early summer favored an increase in rainfall and annual tree growth, while the La Niña phase was associated with less rainfall and reduced tree growth. Extratropical climate factors such as SAM had an equally relevant effect on tree growth, whereby the positive phase of SAM had a negative effect over radial growth. These findings demonstrate the potential for dendroclimatic research and climate reconstruction in a region with scarce tree-ring data. They also improve the understanding of how climate variability may affect woody growth in native forests – an extremely limited ecosystem in the Pampa biome.Dendrochronologia1125-7865 Reuters ISIbiochronology, biome, climate change, climate conditions, climate effect, clonal growth, dendrochronology, dendroclimatology, el nino-southern oscillation, endogenous growth, growth, rainfall, reconstruction, regional climate, subtropical region, temperature effect, tree ring, woody plant, argentina, pampas, rio de la plata, south america, uruguay, scutia buxifolia
Temporal and spatial evaluation of satellite rainfall estimates over different regions in Latin-AmericaBaez-Villanueva, Oscar Manuel; Zambrano-Bigiarini, Mauricio; Ribbe, Lars; Nauditt, Alexandra; Giraldo-Osorio, Juan Diego; Thinh, Nguyen XuanAgua y Extremos2018.010.1016/j.atmosres.2018.05.011Atmospheric Research01698095 Reuters ISIclock and data recovery circuits (cdr circuits), developing countries, efficiency, mean square error, pixels, precipitation (chemical), rain, satellites, time measurement, watersheds, chirpsv2, mswepv2, precipitation patterns, probability of detection, root mean squared errors, spatiotemporal variability, upscaling, validation of sres, rain gages, climate modeling, image analysis, pixel, precipitation assessment, satellite data, spatial resolution, spatiotemporal analysis, trmm, upscaling, colombia, magdalena basin
A plausible atmospheric trigger for the 2017 coastal El Niño: THE 2017 COASTAL EL NIÑOGarreaud, René D.Agua y Extremos2018.010.1002/joc.5426The far eastern tropical Pacific experienced a rapid, marked warming in early 2017, causing torrential rains along the west coast of South America with a significant societal toll in Peru and Ecuador. This strong coastal El Niño was largely unpredicted, even a few weeks before its onset, and it developed differently from either central or eastern events. Here we provide an overview of the event, its impacts and concomitant atmospheric circulation. It is proposed that a remotely forced, sustained weakening of the free tropospheric westerly flow impinging the subtropical Andes leads to a relaxation of the southeasterly (SE) trades off the coast, which in turn may have warmed the eastern Pacific throughout the weakening of upwelling in a near-coastal band and the lessening of the evaporative cooling farther offshore.International Journal of Climatology0899-8418 Reuters ISIevaporative cooling systems, oil well flooding, atmospheric circulation, eastern pacific, eastern tropical pacific, enso, evaporative cooling, peru, south america, torrential rain, nickel, atmospheric circulation, coastal zone, el nino, el nino-southern oscillation, flooding, troposphere, westerly, andes, ecuador, pacific ocean, pacific ocean (tropical), peru
Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CEBüntgen, Ulf; Wacker, Lukas; Galván, J. Diego; Arnold, Stephanie; Arseneault, Dominique; Baillie, Michael; Beer, Jürg; Bernabei, Mauro; Bleicher, Niels; Boswijk, Gretel; Bräuning, Achim; Carrer, Marco; Ljungqvist, Fredrik Charpentier; Cherubini, Paolo; Christl, Marcus; Christie, Duncan A.; Clark, Peter W.; Cook, Edward R.; D’Arrigo, Rosanne; Davi, Nicole; Eggertsson, Ólafur; Esper, Jan; Fowler, Anthony M.; Gedalof, Ze’ev; Gennaretti, Fabio; Grießinger, Jussi; Grissino-Mayer, Henri; Grudd, Håkan; Gunnarson, Björn E.; Hantemirov, Rashit; Herzig, Franz; Hessl, Amy; Heussner, Karl-Uwe; Jull, A. J. Timothy; Kukarskih, Vladimir; Kirdyanov, Alexander; Kolář, Tomáš; Krusic, Paul J.; Kyncl, Tomáš; Lara, Antonio; LeQuesne, Carlos; Linderholm, Hans W.; Loader, Neil J.; Luckman, Brian; Miyake, Fusa; Myglan, Vladimir S.; Nicolussi, Kurt; Oppenheimer, Clive; Palmer, Jonathan; Panyushkina, Irina; Pederson, Neil; Rybníček, Michal; Schweingruber, Fritz H.; Seim, Andrea; Sigl, Michael; Churakova, Olga; Speer, James H.; Synal, Hans-Arno; Tegel, Willy; Treydte, Kerstin; Villalba, Ricardo; Wiles, Greg; Wilson, Rob; Winship, Lawrence J.; Wunder, Jan; Yang, Bao; Young, Giles H. F.Agua y Extremos2018.010.1038/s41467-018-06036-0Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the 14C content in 484 individual tree rings formed in the periods 770–780 and 990–1000 CE. Distinct 14C excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved 14C measurements are needed.Nature Communications2041-1723 Reuters ISIcarbon 14, carbon isotope, chronology, concentration (composition), cosmogenic radionuclide, solar radiation, spatiotemporal analysis, tree ring, article, atmospheric radioactivity, chronology, proton radiation, radiation measurement, radiometric dating, space, spring, summer, weather
Past and future global transformation of terrestrial ecosystems under climate changeNolan, Connor; Overpeck, Jonathan T.; Allen, Judy R. M.; Anderson, Patricia M.; Betancourt, Julio L.; Binney, Heather A.; Brewer, Simon; Bush, Mark B.; Chase, Brian M.; Cheddadi, Rachid; Djamali, Morteza; Dodson, John; Edwards, Mary E.; Gosling, William D.; Haberle, Simon; Hotchkiss, Sara C.; Huntley, Brian; Ivory, Sarah J.; Kershaw, A. Peter; Kim, Soo-Hyun; Latorre, Claudio; Leydet, Michelle; Lézine, Anne-Marie; Liu, Kam-Biu; Liu, Yao; Lozhkin, A. V.; McGlone, Matt S.; Marchant, Robert A.; Momohara, Arata; Moreno, Patricio I.; Müller, Stefanie; Otto-Bliesner, Bette L.; Shen, Caiming; Stevenson, Janelle; Takahara, Hikaru; Tarasov, Pavel E.; Tipton, John; Vincens, Annie; Weng, Chengyu; Xu, Qinghai; Zheng, Zhuo; Jackson, Stephen T.Agua y Extremos2018.010.1126/science.aan5360Impacts of global climate change on terrestrial ecosystems are imperfectly constrained by ecosystem models and direct observations. Pervasive ecosystem transformations occurred in response to warming and associated climatic changes during the last glacial-to-interglacial transition, which was comparable in magnitude to warming projected for the next century under high-emission scenarios. We reviewed 594 published paleoecological records to examine compositional and structural changes in terrestrial vegetation since the last glacial period and to project the magnitudes of ecosystem transformations under alternative future emission scenarios. Our results indicate that terrestrial ecosystems are highly sensitive to temperature change and suggest that, without major reductions in greenhouse gas emissions to the atmosphere, terrestrial ecosystems worldwide are at risk of major transformation, with accompanying disruption of ecosystem services and impacts on biodiversity.Science0036-8075 Reuters ISIbiodiversity, climate change, ecosystem service, glacial-interglacial cycle, global climate, greenhouse gas, last glacial, terrestrial ecosystem, vegetation cover, article, atmosphere, biodiversity, carbon footprint, climate change, ecosystem, biodiversity, biodiversity, climate change
On the evaluation of adaptation practices: a transdisciplinary exploration of drought measures in ChileLillo-Ortega, Gloria; Aldunce, Paulina; Adler, Carolina; Vidal, Marcela; Rojas, MaisaAgua y Extremos; Gobernanza e Interfaz Ciencia y Política2019.010.1007/s11625-018-0619-5A severe drought has affected central Chile since 2009. Various adaptation responses have been developed, and a participatory process is required to learn from them. To enable this, a transdisciplinary approach was adopted to achieve two objectives: first, to test an approach for assessing the effectiveness of existing measures to respond to drought, specifically to distil strengths and weaknesses of implementation, and developing recommendations; second, to reflect on results from a pilot project conducted to ascertain its potential for scalability in terms of processes employed. The research was organized per the three types of knowledge needed to address complex problems through transdisciplinarity: systems, target and transformation knowledge. Using the recent drought as a boundary object, we conducted the pilot in two locations in Chile where we carried out literature reviews, interviews and focus group discussions were carried out. We identified adaptation measures at national and local scale, a set of which were evaluated applying the Index for the Usefulness of Adaptation Practices (IUPA). Results indicate that through IUPA, we could systematically account for the perceived effectiveness of applied measures. Strengths such as autonomy in the decision-making process emerged as key factors that could also be applied in other contexts, whereas weaknesses such as lack of integration with other policy domains, programs or projects were identified. To address weaknesses, key recommendations were proposed, which are congruent with context-specific expectations, capacities, experiences and knowledge, given that they were articulated by local actors. Results present empirical evidence on the important utility of transdisciplinary approaches in the evaluation of adaptation measures and can support the development of metrics related to adaptation process at the local scale.Sustainability Science1862-4065 Reuters ISIchile, drought, evaluation of adaptation, index for the usefulness of adaptation practices (iupa), resilience, transdisciplinarity
Terrain-Trapped Airflows and Orographic Rainfall along the Coast of Northern California. Part II: Horizontal and Vertical Structures Observed by a Scanning Doppler RadarValenzuela, Raul A.; Kingsmill, David E.Agua y Extremos2018.010.1175/MWR-D-17-0227.1This study documents the mean properties and variability of kinematic and precipitation structures associated with orographic precipitation along the coast of Northern California in the context of terrain-trapped airflows (TTAs). TTAs are defined as relatively narrow air masses that consistently flow in close proximity and approximately parallel to an orographic barrier. Seven land-falling winter storms are examined with observations from a scanning X-band Doppler radar deployed on the coast at Fort Ross, California. Additional information is provided by a 915-MHz wind-profiling radar, surface meteorology, a GPS receiver, and balloon soundings. The composite kinematic structure during TTA conditions exhibits a significant horizontal gradient of wind direction from the coast to approximately 50 km offshore and a low-level jet (LLJ) that surmounts a weaker airflow offshore corresponding to the TTA, with a zone of enhanced precipitation evident between ~5 and 25 km offshore and oriented nearly parallel to the coastline. Conversely, the composite kinematic structure during NO-TTA conditions exhibits a smaller offshore horizontal gradient of wind direction and precipitation structures are generally enhanced within ~15 km of the coastline. Interstorm variability analysis reveals significant variations in kinematic structures during both TTA and NO-TTA conditions, whereas significant variations in precipitation structures are only evident during TTA conditions. The interstorm analysis also illustrates more clearly how LLJ vertical structures evident during NO-TTA conditions exhibit ascent along the coast and over the coastal mountains, which is in contrast to TTA conditions where the ascent occurs offshore and over the TTA.Monthly Weather Review0027-0644 Reuters ISIatmospheric movements, channel flow, doppler radar, global positioning system, kinematics, landforms, precipitation (chemical), storms, coastal meteorologies, horizontal gradients, kinematic structures, orographic effects, orographic precipitation, orographic rainfalls, precipitation structure, radars/radar observations, precipitation (meteorology), airflow, channel flow, coastal zone, doppler radar, hydrometeorology, orographic effect, precipitation assessment, rainfall, terrain, wind direction, california, united states
Human–environmental drivers and impacts of the globally extreme 2017 Chilean firesBowman, David M. J. S.; Moreira-Muñoz, Andrés; Kolden, Crystal A.; Chávez, Roberto O.; Muñoz, Ariel A.; Salinas, Fernanda; González-Reyes, Álvaro; Rocco, Ronald; de la Barrera, Francisco; Williamson, Grant J.; Borchers, Nicolás; Cifuentes, Luis A.; Abatzoglou, John T.; Johnston, Fay H.Agua y Extremos2018.010.1007/s13280-018-1084-1In January 2017, hundreds of fires in Mediterranean Chile burnt more than 5000 km2, an area nearly 14 times the 40-year mean. We contextualize these fires in terms of estimates of global fire intensity using MODIS satellite record, and provide an overview of the climatic factors and recent changes in land use that led to the active fire season and estimate the impact of fire emissions to human health. The primary fire activity in late January coincided with extreme fire weather conditions including all-time (1979–2017) daily records for the Fire Weather Index (FWI) and maximum temperature, producing some of the most energetically intense fire events on Earth in the last 15-years. Fire activity was further enabled by a warm moist growing season in 2016 that interrupted an intense drought that started in 2010. The land cover in this region had been extensively modified, with less than 20% of the original native vegetation remaining, and extensive plantations of highly flammable exotic Pinus and Eucalyptus species established since the 1970s. These plantations were disproportionally burnt (44% of the burned area) in 2017, and associated with the highest fire severities, as part of an increasing trend of fire extent in plantations over the past three decades. Smoke from the fires exposed over 9.5 million people to increased concentrations of particulate air pollution, causing an estimated 76 premature deaths and 209 additional admissions to hospital for respiratory and cardiovascular conditions. This study highlights that Mediterranean biogeographic regions with expansive Pinus and Eucalyptus plantations and associated rural depopulation are vulnerable to intense wildfires with wide ranging social, economic, and environmental impacts, which are likely to become more frequent due to longer and more extreme wildfire seasons.Ambio0044-7447 Reuters ISIatmospheric pollution, extreme event, forest fire, health risk, land cover, mediterranean environment, modis, native species, pollution incidence, satellite altimetry, smoke, chile, eucalyptus, chile, drought, fire, human, pine, weather, chile, droughts, fires, humans, pinus, weather
Potencial de los anillos de crecimiento de Pilgerodendron uviferum para el estudio histórico de las Iglesias de Chiloé, Patrimonio de la HumanidadPuchi, Paulina; Muñoz, Ariel A; González, Mauro E; Abarzúa, Ana; Araya, Katerine; Towner, Ronald; Fitzek, Reinhard; Holz, Andrés; Stahle, DanielCambio de Uso de Suelo; Agua y Extremos2017.010.4067/S0717-92002017000100012Las iglesias de Chiloé son antiguas estructuras de madera reconocidas patrimonio de la humanidad por la UNESCO. Gran parte de su historia de construcción y reparaciones aún se desconoce. Considerando que muchas de las iglesias de Chiloé fueron construidas utilizando madera de Pilgerodendron uviferum, el objetivo de este trabajo fue evaluar el potencial de esta especie para datar piezas de madera de dos de estas históricas construcciones: las iglesias de Vilupulli e Ichuac. En Vilupulli se dataron piezas de 311 y 181 años provenientes de los pilares de la torre. Estas piezas fueron fechadas con cronologías de ancho de anillos de P. uviferum cercanas a las dos iglesias. También utilizando estas cronologías se dataron piezas de 79, 89, 97 y 135 años obtenidas a partir de los pilotes que sostienen el piso de la iglesia de Ichuac. Considerando que Vilupulli fue construida a principios del siglo XX, es posible que las muestras de la torre que presentaron fechas cercanas a 1918, sean parte del proceso tardío de construcción de la iglesia o de una restauración posterior. Por su parte, Ichuac fue construida a finales del siglo XIX, por lo que las piezas del piso que dataron entre 19201929, formarían parte de una posible restauración no descrita previamente en archivos históricos, la cual pudo ocurrir incluso varios años posterior a la fecha del anillo más reciente encontrado en las piezas estudiadas. Se concluye que P. uviferum tiene alto potencial para estudios históricos en estructuras patrimoniales en el sur de Chile.Bosque (Valdivia)0717-9200 Reuters ISIdendroarchaeology, historical structures, pilgerodendron uviferum
Modeling study of biomass burning plumes and their impact on urban air quality; a case study of Santiago de ChileCuchiara, G.C.; Rappenglück, B.; Rubio, M.A.; Lissi, E.; Gramsch, E.; Garreaud, R.D.Agua y Extremos2017.010.1016/j.atmosenv.2017.07.002On January 4, 2014, during the summer period in South America, an intense forest and dry pasture wildfire occurred nearby the city of Santiago de Chile. On that day the biomass-burning plume was transported by low-intensity winds towards the metropolitan area of Santiago and impacted the concentration of pollutants in this region. In this study, the Weather Research and Forecasting model coupled with Chemistry (WRF/Chem) is implemented to investigate the biomass-burning plume associated with these wildfires nearby Santiago, which impacted the ground-level ozone concentration and exacerbated Santiago's air quality. Meteorological variables simulated by WRF/Chem are compared against surface and radiosonde observations, and the results show that the model reproduces fairly well the observed wind speed, wind direction air temperature and relative humidity for the case studied. Based on an analysis of the transport of an inert tracer released over the locations, and at the time the wildfires were captured by the satellite-borne Moderate Resolution Imaging Spectroradiometer (MODIS), the model reproduced reasonably well the transport of biomass burning plume towards the city of Santiago de Chile within a time delay of two hours as observed in ceilometer data. A six day air quality simulation was performed: the first three days were used to validate the anthropogenic and biogenic emissions, and the last three days (during and after the wildfire event) to analyze the performance of WRF/Chem plume-rise model within FINNv1 fire emission estimations. The model presented a satisfactory performance on the first days of the simulation when contrasted against data from the well-established air quality network over the city of Santiago de Chile. These days represent the urban air quality base case for Santiago de Chile unimpacted by fire emissions. However, for the last three simulation days, which were impacted by the fire emissions, the statistical indices showed a decrease in the model performance. While the model showed a satisfactory evidence that wildfires plumes that originated in the vicinity of Santiago de Chile were transported towards the urban area and impacted the air quality, the model still underpredicted some pollutants substantially, likely due to misrepresentation of fire emission sources during those days. Potential uncertainties may include to the land use/land cover classifications and its characteristics, such as type and density of vegetation assigned to the region, where the fire spots are detected. The variability of the ecosystem type during the fire event might also play a role.Atmospheric Environment13522310 Reuters ISIair quality, atmospheric humidity, atmospheric temperature, biomass, image reconstruction, meteorological instruments, pollution, radiometers, radiosondes, satellite imagery, weather forecasting, anthropogenic and biogenic emissions, atmospheric model, biomass-burning, ground level ozone concentration, moderate resolution imaging spectroradiometer, plume rise, weather research and forecasting models, wrf/chem, fires, ozone, air quality, anthropogenic effect, atmospheric modeling, atmospheric plume, biogenic emission, biomass burning, forecasting method, metropolitan area, modis, radiosonde, urban pollution, air quality, air temperature, article, biomass, circadian rhythm, combustion, humidity, land use, pasture, plume, priority journal, sensitivity analysis, simulation, summer, urban area, wind, chile, metropolitana, santiago [metropolitana]
Local Perception of Drought Impacts in a Changing Climate: The Mega-Drought in Central ChileAldunce, Paulina; Araya, Dámare; Sapiain, Rodolfo; Ramos, Issa; Lillo, Gloria; Urquiza, Anahí; Garreaud, RenéAgua y Extremos; Gobernanza e Interfaz Ciencia y Política2017.010.3390/su9112053Droughts are a recurrent and complex natural hazard whose frequency and magnitude are expected to increase with climate change. Despite the advances in responding and adapting to droughts (with the development of new policies, for example), droughts continue to cause serious impacts and suffering. Developing well-targeted public policies requires further research on adaptation. Specifically, understanding the public perception of drought can help to identify drivers of and barriers to adaptation and options. This research seeks to understand the public perception of drought in central Chile in order to inform adaptation-related policies and decision-making processes. This study focused on the Mega-drought, which was a protracted dry spell afflicting central Chile since 2010.Sustainability2071-1050 Reuters ISIclimate change, climate effect, decision making, drought, natural hazard, perception, policy development, social policy, chile
The Chilean Coastal Orographic Precipitation Experiment: Observing the Influence of Microphysical Rain Regimes on Coastal Orographic PrecipitationMassmann, Adam K.; Minder, Justin R.; Garreaud, René D.; Kingsmill, David E.; Valenzuela, Raul A.; Montecinos, Aldo; Fults, Sara Lynn; Snider, Jefferson R.Agua y Extremos2017.010.1175/JHM-D-17-0005.1The Chilean Coastal Orographic Precipitation Experiment (CCOPE) was conducted during the austral winter of 2015 (May-August) in the Nahuelbuta Mountains (peak elevation 1.3 km MSL) of southern Chile (38°S). CCOPE used soundings, two profiling Micro Rain Radars, a Parsivel disdrometer, and a rain gauge network to characterize warm and ice-initiated rain regimes and explore their consequences for orographic precipitation. Thirty-three percent of foothill rainfall fell during warm rain periods, while 50% of rainfall fell during ice-initiated periods. Warm rain drop size distributions were characterized by many more and relatively smaller drops than ice-initiated drop size distributions. Both the portion and properties of warm and ice-initiated rainfall compare favorably with observations of coastal mountain rainfall at a similar latitude in California. Orographic enhancement is consistently strong for rain of both types, suggesting that seeding from ice aloft is not a requisite for large orographic enhancement. While the data suggest that orographic enhancement may be greater during warm rain regimes, the difference in orographic enhancement between regimes is not significant. Sounding launches indicate that differences in orographic enhancement are not easily explainable by differences in low-level moisture flux or nondimensional mountain height between the regimes.Journal of Hydrometeorology1525-755X, 1525-7541 Reuters ISIcloud microphysics, coastal zone, marine atmosphere, orographic effect, precipitation (climatology), precipitation assessment, size distribution, stratiform cloud, chile
Research on Climate Change Policies and Rural Development in Latin America: Scope and GapsLocatelli, Bruno; Aldunce, Paulina; Fallot, Abigaïl; Le Coq, Jean-François; Sabourin, Eric; Tapasco, JeimarAgua y Extremos2017.010.3390/su9101831Research on climate change policies can contribute to policy development by building an understanding of the barriers faced in policy processes, and by providing knowledge needed throughout policy cycles. This paper explores the thematic coverage of research on climate change policies related to rural areas, rural development, and natural resource management in Latin America. A three-tier framework is proposed to analyse the selected literature. The results show that research studies have focussed on the mitigation of greenhouse gas emissions from forests, and adaptations to climate change in agriculture. There is little policy research on other vulnerable sectors (e.g., water and health) and emitting sectors (e.g., energy and industry) in the context of rural development. Our analysis highlights the various research gaps that deserve increased scientific attention, including: cross-sector approaches, multi-level governance, and the stages of policy adoption, implementation and evaluation. In addition, the selected literature has a limited contribution to theoretical discussions in policy sciences.Sustainability2071-1050 Reuters ISIadaptive management, climate change, environmental policy, forest edge, greenhouse gas, natural resource, policy development, policy implementation, research work, resource management, rural area, rural development, latin america
Climate change and resilience of deciduous Nothofagus forests in central-east Chilean Patagonia over the last 3200 years: RESILIENCE OF DECIDUOUS NOTHOFAGUS FORESTS IN PATAGONIASimi, E.; Moreno, P. I.; Villa-Martínez, R.; Vilanova, I.; de Pol-Holz, R.Cambio de Uso de Suelo; Agua y Extremos2017.010.1002/jqs.2948We examine the response of Nothofagus forests to climate change and disturbance regimes over the last 3200 years near Coyhaique (45°S), central–east Chilean Patagonia, using fine‐resolution pollen and charcoal records from lake sediment cores. Closed‐canopy deciduous Nothofagus forests have dominated the region with little variation until the arrival of Chilean–European settlers, suggesting a predominance of cool‐temperate and wet conditions. Within this state we identify centennial‐scale episodes of forest fragmentation, increase in littoral macrophytes and volcanic/paleofire disturbance between 2700 and 3000 cal a BP, 2200 and 2500 cal a BP and over the last ∼250 years, which we interpret as intervals with negative hydrologic balance. Natural variability caused little impact on the physiognomy and composition of the vegetation in pre‐European time, in contrast to the accelerated shift that started during the late 19th century associated with deforestation, homogenization and synchronization of ecosystem changes at the landscape level, and spread of exotic plant species brought by Chilean and European settlers during a warm/dry interval. The resilience of deciduous Nothofagus forests to natural disturbance regimes and climate change was exceeded by large‐scale human disturbance since the late 19th century by fire, timber exploitation and livestock grazing. These disturbances caused an ecosystem shift towards artificial meadows and scrublands with frequent high‐magnitude fires.Journal of Quaternary Science0267-8179 Reuters ISIclimate variation, deciduous forest, disturbance, fire history, holocene, human activity, paleoclimate, paleoenvironment, tephra, chile, patagonia, nothofagus
The 2010-2015 mega drought in Central Chile: Impacts on regional hydroclimate and vegetationGarreaud, R.; Alvarez-Garreton, Camila; Barichivich, Jonathan; Boisier, Juan Pablo; Christie, Duncan; Galleguillos, Mauricio; LeQuesne, Carlos; McPhee, James; Zambrano-Bigiarini, MauricioCambio de Uso de Suelo; Agua y Extremos2017.010.5194/hess-21-6307-2017Since 2010 an uninterrupted sequence of dry years, with annual rainfall deficits ranging from 25 to 45 %, has prevailed in Central Chile (western South America, 30–38° S). Although intense 1- or 2-year droughts are recurrent in this Mediterranean-like region, the ongoing event stands out because of its longevity and large spatial extent. The extraordinary character of the so-called Central Chile Mega Drought (MD) was established against century long historical records and a millennial tree-ring reconstruction of regional precipitation. The largest MD-averaged rainfall relative anomalies occurred in the northern, semi-arid sector of central Chile but the event was unprecedented to the south of 35° S. ENSO neutral conditions have prevailed since 2011 (but for the strong El Niño 2015) contrasting with La Niña conditions that often accompanied past droughts. The precipitation deficit diminished the Andean snowpack and resulted in amplified declines (up to 90 %) of river flow, reservoir volumes and groundwater levels along central Chile and westernmost Argentina. In some semiarid basins we also found a conspicuous decrease in the runoff-to-rainfall coefficient. A substantial decrease in vegetation productivity occurred in the shrubland-dominated, northern sector, but a mix of greening and browning patches occurred farther south where irrigated croplands and exotic forest plantations dominate. The ongoing warming in central Chile, making the MD one of the warmest 6-year period on record, may have also contributed to such complex vegetation changes by increasing potential evapotranspiration. The understanding of the nature and biophysical impacts of the MD contributes to preparedness efforts to face a dry, warm future regional climate scenario.Hydrology and Earth System Sciences1027-5606 Reuters ISIclimatology, drought, groundwater, nickel, rain, exotic forest plantations, historical records, irrigated cropland, potential evapotranspiration, precipitation deficits, tree-ring reconstruction, vegetation productivity, western south america, vegetation, agricultural land, drought, el nino, el nino-southern oscillation, groundwater, historical record, la nina, multireservoir system, plantation forestry, potential evapotranspiration, precipitation (climatology), rainfall-runoff modeling, regional climate, river flow, shrubland, snowpack, tree ring, vegetation dynamics, andes, argentina, chile, mediterranean region
Anomalías anatómicas en anillos de crecimiento anuales de Austrocedrus chilensis (D. Don) Pic.-Serm. et Bizzarri en el norte de su rango de distribuciónRojas-Badilla, Moisés; Álvarez, Claudio; Velásquez-Álvarez, Gonzalo; Hadad, Martín; Le Quesne, Carlos; Christie, Duncan A.Agua y Extremos2017.010.4067/S0717-66432017000200269Tree-ring anatomical anomalies have received little attention in southern South American trees, however they can contain valuable intra-annual environmental information. This study addressed for the first time the three most frequent tree- ring anomalies recorded in the northern and oldest known Austrocedrus chilensis forest in central Chile (32-35°S). Three anatomic anomalies described were: partially absent rings, intra-annual bands and frost rings. Partially absent rings resulted from cambial inactivity during a complete growing period and require dendrochronological tools to be detected. Intra- annual bands are consequence of the abundance-shortage of environmental resources during the growing season and can be detected by examining the undefined late-wood boundaries. Frost rings, are caused by extreme low temperatures and are characterized by collapsed cells in the tree-ring growth. Results indicate that the northern most population exhibited the highest rate of absent rings, while the occurrence of intra-annual bands seems to be rather minor in the study area. Finally, frost rings are registered mainly in the younger trees in all three studied sites. These results suggest the potential for future spatio-temporal studies that examine the frequency of these anatomical anomalies in A. chilensis chronologies along its wide geographical distribution. This will complement the current environmental information recorded by its growth rates.Gayana. Botánica0717-6643 Reuters ISIabsent rings, dendrochronology, frost rings, intra-annual bands, wood anatomy
Refinement of the tephrostratigraphy straddling the northern Patagonian Andes (40–41°S): new tephra markers, reconciling different archives and ascertaining the timing of piedmont deglaciationAlloway, Brent V.; Pearce, Nicholas J. G.; Moreno, Patricio I.; Villarosa, Gustavo; Jara, Ignacio A.; Henríquez, Carla A.; Sagredo, Esteban A.; Ryan, Matthew T.; Outes, ValeriaAgua y Extremos2021.010.1002/jqs.3389We describe the stratigraphy, age, geochemistry and correlation of tephra from west to east across the northern Patagonian Andes (c. 40–41°S) with a view to further refining the eruptive history of this region back to the onset of the Last Glacial Termination (~18 cal. ka). Eastwards across the Andes, rhyodacite to rhyolitic tephra markers of dominantly Puyehue-Cordón Caulle source are persistently recognised and provide a stratigraphic context for more numerously erupted intervening tephra of basalt to basaltic–andesite composition. Tephra from distal eruptive centres are also recognised. West of the Andean Cordillera, organic-rich cores from a small closed lake basin (Lago Pichilafquén) reveal an exceptional high-resolution record of lowland vegetation–climate change and eruptive activity spanning the last 15 400 years. Three new rhyodacite tephra (BT6-T1, -T2 and -T4) identified near the base of the Pichilafquén record, spanning 13.2 to 13.9 cal. ka bp, can be geochemically matched with correlatives in basal andic soil sequences closely overlying regolith and/or basement rock. The repetitiveness of this tephrostratigraphy across this Andean transect suggests near-synchronous tephra accretion and onset of up-building soil formation under more stable (revegetating) ground-surface conditions following rapid piedmont deglaciation on both sides of the Cordillera by at least ~14 cal. ka bp.Journal of Quaternary Science0267-8179, 1099-1417 Reuters ISIandes, last glacial termination, northwest patagonia, tephra, volcán puyehue
On the selection of precipitation products for the regionalisation of hydrological model parametersBaez-Villanueva, Oscar M.; Zambrano-Bigiarini, Mauricio; Mendoza, Pablo A.; McNamara, Ian; Beck, Hylke E.; Thurner, Joschka; Nauditt, Alexandra; Ribbe, Lars; Thinh, Nguyen XuanAgua y Extremos2021.010.5194/hess-25-5805-2021Abstract. Over the past decades, novel parameter regionalisation techniques have been developed to predict streamflow in data-scarce regions. In this paper, we examined how the choice of gridded daily precipitation (P) products affects the relative performance of three well-known parameter regionalisation techniques (spatial proximity, feature similarity, and parameter regression) over 100 near-natural catchments with diverse hydrological regimes across Chile. We set up and calibrated a conceptual semi-distributed HBV-like hydrological model (TUWmodel) for each catchment, using four P products (CR2MET, RF-MEP, ERA5, and MSWEPv2.8). We assessed the ability of these regionalisation techniques to transfer the parameters of a rainfall-runoff model, implementing a leave-one-out cross-validation procedure for each P product. Despite differences in the spatio-temporal distribution of P, all products provided good performance during calibration (median Kling–Gupta efficiencies (KGE′s) > 0.77), two independent verification periods (median KGE′s >0.70 and 0.61, for near-normal and dry conditions, respectively), and regionalisation (median KGE′s for the best method ranging from 0.56 to 0.63). We show how model calibration is able to compensate, to some extent, differences between P forcings by adjusting model parameters and thus the water balance components. Overall, feature similarity provided the best results, followed by spatial proximity, while parameter regression resulted in the worst performance, reinforcing the importance of transferring complete model parameter sets to ungauged catchments. Our results suggest that (i) merging P products and ground-based measurements does not necessarily translate into an improved hydrologic model performance; (ii) the spatial resolution of P products does not substantially affect the regionalisation performance; (iii) a P product that provides the best individual model performance during calibration and verification does not necessarily yield the best performance in terms of parameter regionalisation; and (iv) the model parameters and the performance of regionalisation methods are affected by the hydrological regime, with the best results for spatial proximity and feature similarity obtained for rain-dominated catchments with a minor snowmelt component.Hydrology and Earth System Sciences1607-7938 Reuters ISIcatchments, rain, runoff, statistical methods, hydrological regime, modeling parameters, modeling performance, parameter regionalization, parameter regressions, performance, precipitation products, regionalisation, regionalization techniques, spatial proximity, climate models
High ENSO sensitivity in tree rings from a northern population of Polylepis tarapacana in the Peruvian AndesCrispín-DelaCruz, Doris B.; Morales, Mariano.S.; Andreu-Hayles, Laia.; Christie, Duncan.A.; Guerra, Anthony; Requena-Rojas, Edilson. J.Agua y Extremos2022.010.1016/j.dendro.2021.125902Polylepis tarapacana is the highest-elevation tree species worldwide growing between 4000 and 5000 m a.s.l. along the South American Altiplano. P. tarapacana is adapted to live in harsh conditions and has been widely used for drought and precipitation tree-ring based reconstructions. Here, we present a 400-year tree-ring width (TRW) chronology located in southern Peru (17ºS; 69ºW) at the northernmost limit of P. tarapacana tree species distribution. The objectives of this study are to assess tree growth sensitivity of a northern P. tarapacana population to (1) precipitation, temperature and El Niño Southern Oscillation (ENSO) variability; (2) to compare its growth variability and ENSO sensitivity with southern P. tarapacana forests. Our results showed that this TRW record is highly sensitive to the prior summer season (Nov-Jan) precipitation (i.e. positive correlation) when the South American Summer Monsoon (SASM) reaches its maximum intensity in this region. We also found a positive relationship with current year temperature that suggests that radial growth may be enhanced by warm, less cloudy, conditions during the year of formation. A strong positive relationship was found between el Niño 3.4 and tree growth variability during the current growing season, but negative during the previous growth period. Growth variability in our northern study site was in agreement with other populations that represent almost the full range of P. tarapacana latitudinal distribution (~ 18ºS to 23ºS). Towards the south of the P. tarapacana TRW network there was a decrease in the strength of the agreement of growth variability with our site,with the exception of higher correlation with the two southeastern sites. Similarly, the TRW chronologies recorded higher sensitivity to ENSO influences in the north and southeastern locations, which are wetter, than the drier southwestern sites. These patterns hold for the entire period, as well as for periods of high and low ENSO activity. Overall, P. tarapacana tree growth at the north of its distribution is mostly influenced by prior year moisture availability and current year temperature that are linked to large-scale climate patterns such as the SASM and ENSO, respectively.Dendrochronologia11257865 Reuters ISIpolylepis tarapacana
Water allocation under climate changeBarría, Pilar; Sandoval, Ignacio Barría; Guzman, Carlos; Chadwick, Cristián; Alvarez-Garreton, Camila; Díaz-Vasconcellos, Raúl; Ocampo-Melgar, Anahí; Fuster, RodrigoAgua y Extremos2021.010.1525/elementa.2020.00131Chile is positioned in the 20th rank of water availability per capita. Nonetheless, water security levels vary across the territory. Around 70% of the national population lives in arid and semiarid regions, where a persistent drought has been experienced over the last decade. This has led to water security problems including water shortages. The water allocation and trading system in Chile is based on a water use rights (WURs) market, with limited regulatory and supervisory mechanisms, where the volume to be granted as permanent and eventual WURs is calculated from statistical analyses of historical streamflow records if available, or from empirical estimations if they are not. This computation of WURs does not consider the nonstationarity of hydrological processes nor climatic projections. This study presents the first large sample diagnosis of water allocation system in Chile under climate change scenarios. This is based on novel anthropic intervention indices (IAI), which were computed as the ratio between the total granted water volume to the water availability within 87 basins in north-central and southern Chile (30°S–42°S). The IAI were evaluated for the historical period (1979–2019) and under modeled-based climatic projections (2055–2080). According to these IAI levels, to date, there are 20 out of 87 overallocated basins, which under the assumption that no further WURs will be granted in the future, increases up to 25 basins for the 2055–2080 period. The results show that, to date most of north-central Chilean catchments already have a large anthropic intervention degree, and the increases for the future period occurs mostly in the southern region of the country (approximately 38°S), which has been considered as possible source of water for large water transfer projects (i.e., water roads). These indices and diagnosis are proposed as a tool to help policy makers to address water scarcity under climate change.Elementa: Science of the Anthropocene2325-1026 Reuters ISIclimate change, policy making, streamflow, water availability, water storage, water use, chile
Different climate sensitivity for radial growth, but uniform for tree-ring stable isotopes along an aridity gradient in Polylepis tarapacana , the world’s highest elevation tree speciesRodriguez-Caton, Milagros; Andreu-Hayles, Laia; Morales, Mariano S; Daux, Valérie; Christie, Duncan A; Coopman, Rafael E; Alvarez, Claudio; Rao, Mukund Palat; Aliste, Diego; Flores, Felipe; Villalba, RicardoAgua y Extremos2021.010.1093/treephys/tpab021Abstract Tree growth is generally considered to be temperature limited at upper elevation treelines, yet climate factors controlling tree growth at semiarid treelines are poorly understood. We explored the influence of climate on stem growth and stable isotopes for Polylepis tarapacana Philipi, the world’s highest elevation tree species, which is found only in the South American Altiplano. We developed tree-ring width index (RWI), oxygen (δ18O) and carbon (δ13C) chronologies for the last 60 years at four P. tarapacana stands located above 4400 m in elevation, along a 500 km latitude aridity gradient. Total annual precipitation decreased from 300 to 200 mm from the northern to the southern sites. We used RWI as a proxy of wood formation (carbon sink) and isotopic tree-ring signatures as proxies of leaf-level gas exchange processes (carbon source). We found distinct climatic conditions regulating carbon sink processes along the gradient. Current growing-season temperature regulated RWI at northern-wetter sites, while prior growing-season precipitation determined RWI at arid southern sites. This suggests that the relative importance of temperature to precipitation in regulating tree growth is driven by site water availability. By contrast, warm and dry growing seasons resulted in enriched tree-ring δ13C and δ18O at all study sites, suggesting that similar climate conditions control carbon-source processes along the gradient. Site-level δ13C and δ18O chronologies were significantly and positively related at all sites, with the strongest relationships among the southern drier stands. This indicates an overall regulation of intercellular carbon dioxide via stomatal conductance for the entire P. tarapacana network, with greater stomatal control when aridity increases. This manuscript also highlights a coupling (decoupling) between physiological processes at leaf level and wood formation as a function of similarities (differences) in their climatic sensitivity. This study contributes to a better understanding and prediction of the response of high-elevation Polylepis woodlands to rapid climate changes and projected drying in the Altiplano.Tree Physiology1758-4469 Reuters ISIaridity, carbon dioxide, carbon sink, gas exchange, growth, shrub, stable isotope, stomatal conductance, tree ring, water availability, altiplano, polylepis, polylepis tarapacana, carbon, oxygen, chemistry, forest, tree, wood, carbon isotopes, forests, oxygen isotopes, trees, wood
Chemical Signals in Tree Rings from Northern Patagonia as Indicators of Calbuco Volcano Eruptions since the 16th CenturyBertin, Lizette J.; Christie, Duncan A.; Sheppard, Paul R.; Muñoz, Ariel A.; Lara, Antonio; Alvarez, ClaudioCambio de Uso de Suelo; Ciudades Resilientes; Agua y Extremos2021.010.3390/f12101305The Calbuco volcano ranks third in the specific risk classification of volcanoes in Chile and has a detailed eruption record since 1853. During 2015, Calbuco had a sub-Plinian eruption with negative impacts in Chile and Argentina, highlighting the need to determine the long-term history of its activity at a high-resolution time scale to obtain a better understanding of its eruptive frequency. We developed a continuous eruptive record of Calbuco for the 1514–2016 period by dendrochemical analysis of Fitzroya cupressoides tree rings at a biennium resolution using inductively coupled plasma–mass spectrometry. After comparing the chemical record of 20 elements contained in tree rings with historical eruptions, one group exhibited positive anomalies during (Pb/Sn) and immediately after (Mo/P/Zn/Cu) eruptions, with a Volcanic Explosivity Index (VEI) ≥ 3, and so were classified as chemical tracers of past eruptions (TPE). The tree-ring width chronology also exhibited significant decreases in tree growth associated with eruptions of VEI ≥ 3. According to these records, we identified 11 new eruptive events of Calbuco, extending its eruptive chronology back to the 16th century and determining a mean eruptive frequency of ~23 years. Our results show the potential to use dendrochemical analysis to infer past volcanic eruptions in Northern Patagonia. This information provides a long-term perspective for assessing eruptive history in Northern Patagonia, with implications for territorial planning.Forests1999-4907 Reuters ISIforestry, indicators (chemical), inductively coupled plasma, mass spectrometry, chemical signals, fitzroya cupressoides, inductively coupled plasma-mass spectrometry, northern patagonia, risk classification, sub-plinian eruption, tree rings, volcanic eruptions, volcanic explosivity indices, volcano eruptions, volcanoes, chemical analysis, dendrochronology, inductively coupled plasma method, pine, plinian eruption, sixteenth century, territorial planning, tree ring, chemicals, forestry, frequency, patagonia, records, resolution, rings, trees, argentina, chile, patagonia, fitzroya cupressoides
The South Pacific Pressure Trend Dipole and the Southern BlobGarreaud, René D.; Clem, Kyle; Veloso, José VicencioAgua y Extremos2021.010.1175/JCLI-D-20-0886.1During the last four decades, the sea level pressure has been decreasing over the Amundsen–Bellingshausen Sea (ABS) region and increasing between 30° and 40°S from New Zealand to Chile, thus forming a pressure trend dipole across the South Pacific. The trends are strongest in austral winter and have influenced the climate of West Antarctica and South America. The pressure trends have been attributed to decadal variability in the tropics, expansion of the Hadley cell, and an associated positive trend of the southern annular mode, but these mechanisms explain only about half of the pressure trend dipole intensity. Experiments conducted with two atmospheric models indicate that upper ocean warming over the subtropical southwest Pacific (SSWP), termed the Southern Blob, accounts for about half of the negative pressure trend in the ABS region and nearly all the ridging/drying over the eastern subtropical South Pacific, thus contributing to the central Chile megadrought. The SSWP warming intensifies the pressure trend dipole through warming the troposphere across the subtropical South Pacific and shifting the midlatitude storm track poleward into the ABS. Multidecadal periods of strong SSWP warming also appear in fully coupled preindustrial simulations, associated with a pressure trend dipole and reduction in rainfall over the central tropical Pacific, thus suggesting a natural origin of the Southern Blob and its teleconnection. However, the current warming rate exceeds the range of natural variability, implying a likely additional anthropogenic contribution.Journal of Climate0894-8755, 1520-0442 Reuters ISIsea level, anthropogenic contribution, atmospheric model, decadal variability, mid-latitude storms, natural variability, negative pressures, sea level pressure, southern annular mode, tropics, annual variation, climate change, general circulation model, sea level pressure, seasonal variation, southern hemisphere, trend analysis, amundsen sea, bellingshausen sea, chile, new zealand, southern ocean