East Antarctic Ice Sheet instability: insights from a > 50 ka sediment record from the Vestfold Hills

Geological fieldwork in the Vestfold Hills, a 413 km² ice-free area on the eastern margin of Prydz Bay, Antarctica, was carried out during the R/V Polarstern cruise PS140 to support the research objectives of the Eastern Antarctic Ice Sheet Instabilities (EASI) initiative. A 12 m sediment core composite obtained from Watts Lake provides a high-resolution record of the climatic, glacial, and relative sea-level history of the region, as well as the first evidence of ice-free conditions in the Vestfold Hills prior to the Last Glacial Maximum (LGM). A series of 24 radiocarbon ages from bulk organic carbon, mollusk shells, and lacustrine moss remains collected throughout the core will provide the basis for a detailed age-depth model going back over 50 ka, and provide insight into the rate and timing of deglaciation ~10 ka. Ongoing biogeochemical analyses, including XRF, biomarker, TOC and CNS profiling, will provide proxies for biological productivity and changes in meltwater supply, allowing us to reconstruct Holocene climate trends. A combination of radiocarbon ages from surrounding marine terraces, field geodetic data, and lacustrine-marine transitions identified and dated in the core will allow us to develop updated relative sea level curves that are prerequisites to track isostatic uplift during deglaciation and model past ice thickness. These data will be integrated with other sediment records from the same field campaign, collected along a 10 km E-W transect of the adjacent Ellis Fjord, which will provide further spatial and temporal detail on deglaciation processes and evaluate possible ice readvances in the Vestfold Hills. Overall, the results will improve our understanding of the dynamics of the East Antarctic Ice Sheet and its role in a warming world.