Antarctic Ice Sheet re-advance during the Antarctic Cold Reversal identified in the Western Ross Sea

Abstract

Marine geophysical data collected from the Ross Sea continental shelf during several oceanographic expeditions enabled evaluation of the Last Glacial Maximum (LGM) extent of the Antarctic Ice Sheet (AIS) through the presence of large Grounding Zone Wedges (GZWs), particularly evident in the outer reaches of the Drygalski and Joides basins to the north of Coulman Island. Seismo-stratigraphic observations confirmed by geomorphological and stratigraphic data show a deep grounding line embayment dating back to the early deglacial transition, which preceded the last rapid sea-level and atmospheric CO2 rise. In this work, a new reconstruction based on the analysis of morpho- bathymetric and seismic reflection data from the middle reaches of the Drygalski Basin shows that the post-LGM retreat was followed by a short-lived re-advance of the grounding line during the Antarctic Cold Reversal (ACR). Evidences include GZWs that partly overprint megascale glacial lineations associated with the Coulman Island grounding line, followed by a Holocene retreat phase, which caused the final southward withdrawal of the grounded and floating ice. This late re-advance suggests a significant impact on the extent and thickness of the grounded ice from relatively small amplitude climate oscillations, able to exert a significant control on the AIS during the latest Pleistocene (i.e. the Last Glacial Termination). Given that the marine-based portion of the AIS in the Ross Sea was sensitive to millennial-scale climate oscillations, this evidence will contribute to clarify how the ice sheet may respond to ongoing and future climate change.