@article{SantamansCordobaFrancoetal.2021, author = {Santamans, Carla Daniela and Cordoba, Francisco E. and Franco, Mar{\´i}a G. and Vignoni, Paula and Lupo, Liliana C.}, title = {Hydro-climatological variability in Lagunas de Vilama System, Argentinean Altiplano-Puna Plateau, Southern Tropical Andes (22 degrees S) and its response to large-scale climate forcings}, series = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, volume = {767}, journal = {The science of the total environment : an international journal for scientific research into the environment and its relationship with man}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0048-9697}, doi = {10.1016/j.scitotenv.2020.144926}, pages = {19}, year = {2021}, abstract = {The Altiplano-Puna Plateau holds several shallow lakes, which are very sensitive to climate changes. This work is focused on a high-altitude lake system called Lagunas de Vilama (LVS), located in a complex climatic transition area with scarcity of continuous and homogeneous instrumental records. The objective of this study is to determine the regional spatial-temporal variability of precipitation and evaluate the seasonal and interannual lake responses. We use a lake-surfaces record derived from Landsat images to investigate links with regional precipitations and different climatic forcings. The results reveal that austral summer and autumn precipitations control the variability of the annual lake-surfaces. Also, we found intra-annual and interannual lags in the lake responses to precipitations, and identified several wet and dry stages. Our results show negative trends in precipitations and lake-surfaces, whose were strengthened by a shift to a warm phase of the Atlantic Multidecadal Oscillation in the 1990s. The El Nino Southern Oscillation, Pacific Decadal Oscillation, and Southern Annular Mode also exert a strong influence in the region. This study demonstrates that the variability of LVS lakes is strongly related to the South American Monsoon System dynamics and large-scale climate fordngs from the Pacific and Atlantic Oceans. This work provides novel indices which demonstrated to be good indicators of regional hydroclimatological variability for this region of South America.}, language = {en} } @article{LunaBookhagenNiedermannetal.2018, author = {Luna, Lisa Victoria and Bookhagen, Bodo and Niedermann, Samuel and Rugel, Georg and Scharf, Andreas and Merchel, Silke}, title = {Glacial chronology and production rate cross-calibration of five cosmogenic nuclide and mineral systems from the southern Central Andean Plateau}, series = {Earth \& planetary science letters}, volume = {500}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2018.07.034}, pages = {242 -- 253}, year = {2018}, abstract = {Glacial deposits on the high-altitude, arid southern Central Andean Plateau (CAP), the Puna in northwestern Argentina, document past changes in climate, but the associated geomorphic features have rarely been directly dated. This study provides direct age control of glacial moraine deposits from the central Puna (24 degrees S) at elevations of 3900-5000 m through surface exposure dating with cosmogenic nuclides. Our results show that the most extensive glaciations occurred before 95 ka and an additional major advance occurred between 46 and 39 ka. The latter period is synchronous with the highest lake levels in the nearby Pozuelos basin and the Minchin (Inca Huasi) wet phase on the Altiplano in the northern CAP. None of the dated moraines produced boulder ages corresponding to the Tauca wet phase (24-15 ka). Additionally, the volcanic lithologies of the deposits allow us to establish production ratios at low latitude and high elevation for five different nuclide and mineral systems: Be-10, Ne-21, and Al-26 from quartz (11 or 12 samples) and He-3 and Ne-21 from pyroxene (10 samples). We present production ratios for all combinations of the measured nuclides and cross-calibrated production rates for 21Ne in pyroxene and quartz for the high, (sub-)tropical Andes. The production rates are based on our Be-10-normalized production ratios and a weighted mean of reference 10Be production rates calibrated in the high, tropical Andes (4.02 +/- 0.12 at g(-1) yr(-1)). These are, Ne-21(qtz): 18.1 +/- 1.2 at g(-1) yr(-1) and Ne-21(px): 36.6 +/- 1.8 at g(-1) yr(-1) (En(88-94)) scaled to sea level and high latitude using the Lal/Stone scheme, with 1 sigma uncertainties. As He-3 and Al-26 have been directly calibrated in the tropical Andes, we recommend using those rates. Finally, we compare exposure ages calculated using all measured cosmogenic nuclides from each sample, including 11 feldspar samples measured for Cl-36, and a suite of previously published production rates. (C) 2018 Published by Elsevier B.V.}, language = {en} } @article{ApaesteguiCruzVuilleetal.2018, author = {Apaestegui, James and Cruz, Francisco William and Vuille, Mathias and Fohlmeister, Jens Bernd and Carlo Espinoza, Jhan and Sifeddine, Abdelfettah and Strikis, Nicolas and Guyot, Jean Loup and Ventura, Roberto and Cheng, Hai and Edwards, R. Lawrence}, title = {Precipitation changes over the eastern Bolivian Andes inferred from speleothem (delta O-18) records for the last 1400 years}, series = {Earth \& planetary science letters}, volume = {494}, journal = {Earth \& planetary science letters}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0012-821X}, doi = {10.1016/j.epsl.2018.04.048}, pages = {124 -- 134}, year = {2018}, abstract = {Here we present high-resolution delta O-18 records obtained from speleothems collected in the eastern Bolivian Andes. The stable isotope records are related to the regional- to large-scale atmospheric circulation over South America and allow interpreting changes in delta O-18 during the last 1400 yr as a function of changes in precipitation regimes over the southern tropical Andes. Two distinct phases with more negative delta O-18 values, interpreted as periods of increased convective activity over the eastern Andean Cordillera in Bolivia are observed concomitantly with periods of global climate anomalies during the last millennium, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) respectively. Changes in the Bolivian delta O-18 record during the LIA are apparently related to a southward displacement of the Intertropical Convergence Zone (ITCZ), which acts as a main moisture driver to intensify convection over the tropical continent. During the MCA, however, the increased convective activity observed in the Bolivian record is likely the result of a different mechanism, which implies moisture sourced mainly from the southern tropical Atlantic. This interpretation is consistent with paleoclimate records further to the north in the tropical Andes that show progressively drier conditions during this time period, indicating a more northerly position of the ITCZ. The transition period between the MCA and the LIA shows a slight tendency toward increased delta O-18 values, indicating weakened convective activity. Our results also reveal a non-stationary anti-phased behavior between the delta O-18 reconstructions from Bolivia and northeastern Brazil that confirms a continental-scale east-west teleconnection across South America during the LIA.}, language = {en} }