Marine drivers and consequences of East Antarctic ice sheet instability in the Indian Sector of the Southern Ocean (Acronym: MarEASI)

• Applicant: Professorin Dr. Julia Gottschalk
• Subject Area: Geology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542079859

Only recently was the stability of the East Antarctic ice sheet (EAIS) recognized as one major tipping point in the global climate system because of two reasons: firstly, the EAIS stores vast amounts of water, and has the potential to substantially raise eustatic sea level by several meters upon destabilization; and secondly, it may sensitively respond to ocean warming underneath East Antarctic ice shelves, including regions grounded below sea level such as in the Aurora and Wilkes Subglacial Basins. Despite its importance for global climate, the exact nature and timing of past EAIS instabilities in response to ocean and atmospheric warming are poorly understood for various climate boundary conditions, which makes robust projections of the future impacts of EAIS dynamics difficult. Rooted in the dearth of observations from the East Antarctic margin and the Indian Southern Ocean, a major gap in our understanding of Southern Ocean-East Antarctic ice sheet/shelf interactions are the mechanisms and spatio-temporal scales of EAIS retreat, and the consequences EAIS instabilities has on the Southern Ocean. As part of the multi-disciplinary German EASI (East Antarctic ice Sheet Instability)-Consortium, RV Polarstern will retrieve new sediment cores from the Indian Southern Ocean (eastern Antarctic-Australian Basin) and the East Antarctic slope/shelf-region off Aurora Subglacial Basin (87–112°E) that so far remains strongly understudied. The proposed research project will make use of these unique sediment core archives and will 1) assess changes in Circumpolar Deep Water (CDW) temperature and CDW interactions with East Antarctic ice margins (primarily through bottom water temperature estimates at sites bathed in CDW) and 2) study variations in Southern Ocean CDW upwelling and the release of heat and CO2 to the atmosphere (through multi-proxy reconstructions of CDW oxygenation, ventilation ages and sea surface temperature at the same sites). Paleo-constraints of atmospheric and oceanic drivers of EAIS changes will further be combined with an assessment of 3) the impacts of EAIS instabilities on the Southern Ocean by reconstructing meltwater supply and perturbations in Antarctic Bottom Water (AABW) formation (via seawater salinity and AABW oxygenation at sites bathed in AABW). The focus will lie on the last two glacial periods, the Holocene Thermal Maximum (HTM; 11–5 kyr before present) and the climatic optimum of the last interglacial period, Marine Isotope Stage (MIS) 5e (129–116 kyr before present), in order to investigate relevant extreme scenarios in EAIS dynamics. The research will provide crucial insights into past polar processes, impacts and mechanisms linking the ocean and EAIS dynamics, particularly their sensitivity to climate warming, which is urgently needed to better assess the potential for destabilization of EAIS and global climatic impacts through numerical Earth system models.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: Australia, France
• Cooperation Partners: Professorin Zanna Chase; Dr. Elisabeth Michel; Dr. Taryn Noble