Re-evaluating Holocene ice-sheet thinning in the Indian Ocean sector of East Antarctica based on sea-level data and glacial isostatic adjustment modelling

The study of past changes in East Antarctic Ice Sheet (EAIS) is crucial for understanding the ice-sheet dynamics and its response to the Earth's climate system. Field-based geological data and various model simulations, such as the ice-sheet and glacial isostatic adjustment (GIA) modelling, provide insights into the behaviour of the EAIS changes. Recent studies of in-situ cosmogenic nuclide surface exposure dates have revealed that large-scale thinning occurred in the Dronning Maud Land and Enderby Land of East Antarctica during 9–6 ka. However, the timing of this EAIS thinning event requires a refinement of the ICE-6G model, which is a widely used GIA-based ice-sheet history. To account for this temporal discrepancy of approximately 2,000 years, in which the ICE-6G model predicts ice thinning earlier than indicated by surface exposure dates, it is necessary to compare the sea levels by the GIA modelling with the geological sea-level data to evaluate the validity of this refinement. We established the sea-level dataset by recalibrating radiocarbon dates of previous works and incorporating 13 new sea-level data. The results of the refined ICE-6G model produced the higher Holocene sea-level peaks in the Lützow–Holm Bay, Dronning Maud Land, showing better consistency with sea-level data than the original ICE-6G model. Additionally, the refinements increase the vertical rate of uplift in the Lützow–Holm Bay, making it more consistent with reported GNSS observations. These findings demonstrate that the Holocene rapid ice sheet thinning is corroborated not only by surface exposure dates but also by sea-level data, thus validating the refinement and supporting the mechanism of warm water inflow driven by sea-level highstands, as proposed in previous study.