Climatic influence of the latest Antarctic isotope maximum of the last glacial period (AIM4) on Southern Patagonia
Résumé
This paper presents the first detailed paleoclimate reconstruction of the latest Antarctic isotope maximum (AIM4, similar to 33-29 ka cal. BP) at 52 degrees S in continental southeastern Argentine Patagonia. High-resolution sedimentological and geochemical analyses of sediments from the maar lake Potrok Aike (PTA) reveal a decrease in the thickness of flood-induced turbidites and a series of wind burst deposits during AIM4, both pointing to increasingly drier conditions. This interpretation is also supported by a significant amount of runoff-driven micropumices incorporated within the sediments that suggests a lower lake level with canyons incising thick tephra deposits around the lake. Increased gustiness and/or dust availability in southeast Patagonia, together with intensified Antarctic circumpolar circulation in the Drake Passage, dust deposition in the Scotia Sea and in Antarctica ice shelf, are consistent with a southward shift of the Southern Westerly Winds (SWW) during the AIM4. In contrast to other warmer AlMs, the SWW during the AIM4 did not migrate far enough south to generate upwelling in the Southern Ocean and they did not reach 52 S in SE Patagonia, as revealed by unchanged values of the rock-magnetic proxy of wind intensity obtained from the same PTA core. Nevertheless, the SWW displacement during AIM4 imposed drier conditions at 52 S in southeast Patagonia likely by blocking precipitation from the Atlantic Ocean, in a way similar to modem seasonal variations and the other Antarctic warm events. (C) 2017 Elsevier B.V. All rights reserved.