Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation

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 prop...

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Autores principales:	Tancrède P. M. Leger, Andrew S. Hein, Daniel Goldberg, Irene Schimmelpfennig, Maximillian S. Van Wyk de Vries, Robert G. Bingham, ASTER Team, Georges Aumaitre
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	Patagonia glaciers and climate last glacial termination cosmogenic nuclide surface exposure dating glacier modelling southern westerly winds Science Q
Acceso en línea:	https://doaj.org/article/3c4104214cfe4bdeaffaccb95d63ca0a
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spelling	oai:doaj.org-article:3c4104214cfe4bdeaffaccb95d63ca0a2021-11-09T07:02:44ZNortheastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation2296-646310.3389/feart.2021.751987https://doaj.org/article/3c4104214cfe4bdeaffaccb95d63ca0a2021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/feart.2021.751987/fullhttps://doaj.org/toc/2296-6463The 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 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.Tancrède P. M. LegerAndrew S. HeinDaniel GoldbergIrene SchimmelpfennigMaximillian S. Van Wyk de VriesRobert G. Bingham ASTER TeamGeorges AumaitreFrontiers Media S.A.articlePatagoniaglaciers and climatelast glacial terminationcosmogenic nuclide surface exposure datingglacier modellingsouthern westerly windsScienceQENFrontiers in Earth Science, Vol 9 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Patagonia glaciers and climate last glacial termination cosmogenic nuclide surface exposure dating glacier modelling southern westerly winds Science Q
spellingShingle	Patagonia glaciers and climate last glacial termination cosmogenic nuclide surface exposure dating glacier modelling southern westerly winds Science Q Tancrède P. M. Leger Andrew S. Hein Daniel Goldberg Irene Schimmelpfennig Maximillian S. Van Wyk de Vries Robert G. Bingham ASTER Team Georges Aumaitre Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation
description	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 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.
format	article
author	Tancrède P. M. Leger Andrew S. Hein Daniel Goldberg Irene Schimmelpfennig Maximillian S. Van Wyk de Vries Robert G. Bingham ASTER Team Georges Aumaitre
author_facet	Tancrède P. M. Leger Andrew S. Hein Daniel Goldberg Irene Schimmelpfennig Maximillian S. Van Wyk de Vries Robert G. Bingham ASTER Team Georges Aumaitre
author_sort	Tancrède P. M. Leger
title	Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation
title_short	Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation
title_full	Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation
title_fullStr	Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation
title_full_unstemmed	Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation
title_sort	northeastern patagonian glacier advances (43°s) reflect northward migration of the southern westerlies towards the end of the last glaciation
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/3c4104214cfe4bdeaffaccb95d63ca0a
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Northeastern Patagonian Glacier Advances (43°S) Reflect Northward Migration of the Southern Westerlies Towards the End of the Last Glaciation

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