TY - JOUR
T1 - Northeastern Patagonian glacier advances (43°S) reflect northward migration of the Southern Westerlies towards the end of the last glaciation
AU - Leger , Tancrède
AU - Hein, Andy
AU - Goldberg, Daniel
AU - Schimmelpfennig, Irene
AU - Van Wyk de Vries, Maximilian S.
AU - Bingham, Robert G.
N1 - © 2021 Leger, Hein, Goldberg, Schimmelpfennig, Van Wyk de Vries and Bingham. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)
This investigation is part of a University of Edinburgh E3 Doctoral Training Partnership Ph.D. studentship (award code: NE/L002558/1) awarded by the National Environment Research Council (NERC) to TPML. Our 2020 field expedition was supported by a crowd-funding campaign through the Crowd.Science fundraising platform (https://crowd.science) and a British Society for Geomorphology Postgraduate Research Grant award (BSG-2019-04) awarded to TPML in October 2019. TCN dating laboratory analyses and AMS measurements were partly funded by a Scottish Alliance for Geoscience, Environment and Society (SAGES) small grant scheme awarded to TPML in August 2020.
PY - 2021/11/9
Y1 - 2021/11/9
N2 - The last glacial termination was a key event during Earth’s Quaternary history that was associated with rapid, high-magnitude environmental and climatic change. Identifying its trigger mechanisms is critical for understanding Earth’s modern climate system over millennial timescales. It has been proposed that latitudinal shifts of the Southern Hemisphere Westerly Wind belt and the coupled Subtropical Front are important components of the changes leading to global deglaciation, making them essential to investigate and reconstruct empirically. The Patagonian Andes are part of the only continental landmass that fully intersects the Southern Westerly Winds, and thus present an opportunity to study their former latitudinal migrations through time and to constrain southern mid-latitude palaeo-climates. Here we use a combination of geomorphological mapping, terrestrial cosmogenic nuclide exposure dating and glacial numerical modelling to reconstruct the late-Last Glacial Maximum (LGM) behaviour and surface mass balance of two mountain glaciers of northeastern Patagonia (43°S, 71°W), the El Loro and Río Comisario palaeo-glaciers. In both valleys, we find geomorphological evidence of glacier advances that occurred after the retreat of the main ice-sheet outlet glacier from its LGM margins. We date the outermost moraine in the El Loro valley to 18.0 ± 1.15 ka. Moreover, a series of moraine-matching simulations were run for both glaciers using a spatially-distributed ice-flow model coupled with a positive degree-day surface mass balance parameterisation. Following a correction for cumulative local surface uplift resulting from glacial isostatic adjustment since ~18 ka, which we estimate to be ~130 m, the glacier model suggests that regional mean annual temperatures were between 1.9 °C and 2.8 °C lower than present at around 18.0 ± 1.15 ka, while precipitation was between ~50% and ~380% higher than today. Our findings support the proposed equatorward migration of the precipitation-bearing Southern Westerly Wind belt towards the end of the LGM, between ~19.5 and ~18 ka, which caused more humid conditions towards the eastern margins of the northern Patagonian Ice Sheet a few centuries ahead of widespread deglaciation across the cordillera.
AB - The last glacial termination was a key event during Earth’s Quaternary history that was associated with rapid, high-magnitude environmental and climatic change. Identifying its trigger mechanisms is critical for understanding Earth’s modern climate system over millennial timescales. It has been proposed that latitudinal shifts of the Southern Hemisphere Westerly Wind belt and the coupled Subtropical Front are important components of the changes leading to global deglaciation, making them essential to investigate and reconstruct empirically. The Patagonian Andes are part of the only continental landmass that fully intersects the Southern Westerly Winds, and thus present an opportunity to study their former latitudinal migrations through time and to constrain southern mid-latitude palaeo-climates. Here we use a combination of geomorphological mapping, terrestrial cosmogenic nuclide exposure dating and glacial numerical modelling to reconstruct the late-Last Glacial Maximum (LGM) behaviour and surface mass balance of two mountain glaciers of northeastern Patagonia (43°S, 71°W), the El Loro and Río Comisario palaeo-glaciers. In both valleys, we find geomorphological evidence of glacier advances that occurred after the retreat of the main ice-sheet outlet glacier from its LGM margins. We date the outermost moraine in the El Loro valley to 18.0 ± 1.15 ka. Moreover, a series of moraine-matching simulations were run for both glaciers using a spatially-distributed ice-flow model coupled with a positive degree-day surface mass balance parameterisation. Following a correction for cumulative local surface uplift resulting from glacial isostatic adjustment since ~18 ka, which we estimate to be ~130 m, the glacier model suggests that regional mean annual temperatures were between 1.9 °C and 2.8 °C lower than present at around 18.0 ± 1.15 ka, while precipitation was between ~50% and ~380% higher than today. Our findings support the proposed equatorward migration of the precipitation-bearing Southern Westerly Wind belt towards the end of the LGM, between ~19.5 and ~18 ka, which caused more humid conditions towards the eastern margins of the northern Patagonian Ice Sheet a few centuries ahead of widespread deglaciation across the cordillera.
U2 - 10.3389/feart.2021.751987
DO - 10.3389/feart.2021.751987
M3 - Article
SN - 2296-6463
JO - Frontiers in Earth Science
JF - Frontiers in Earth Science
ER -