| Summary: | The recent disintegration of AntarcticPeninsula ice shelves, and the associated accelerated discharge and retreat of continental glaciers, has highlighted the necessity of quantifying the current rate of Antarctic ice mass loss and the regional contributions to future sea-level rise. Observations of present day ice mass change need to be corrected for ongoing glacial isostaticadjustment, a process which must be constrained by geological data. However, there are relatively little geological data on the geometry, volume and melt history of the AntarcticPeninsula Ice Sheet (APIS) after Termination 1, and during the Holocene so the glacial isostatic correction remains poorly constrained. To address this we provide field constraints on the timing and rate of APIS deglaciation, and changes in relativesea-level (RSL) for the north-eastern AntarcticPeninsula based on geomorphological evidence of former marine limits, and radiocarbon-dated marine-freshwater transitions from a series of isolation basins at different altitudes on Beak Island. Relativesea-level fell from a maximum of c. 15 m above present at c. 8000 cal yr BP, at a rate of 3.91 mm yr−1 declining to c. 2.11 mm yr−1 between c. 6900–2900 cal yr BP, 1.63 mm yr−1 between c. 2900–1800 cal yr BP, and finally to 0.29 mm yr−1 during the last c. 1800 years. The new Beak Island RSL curve improves the spatial coverage of RSL data in the Antarctic. It is in broad agreement with some glacio-isostaticadjustmentmodels applied to this location, and with work undertaken elsewhere on the AntarcticPeninsula. These geological and RSL constraints from Beak Island imply significant thinning of the north-eastern APIS by the early Holocene. Further, they provide key data for the glacial isostatic correction required by satellite-derived gravity measurements of contemporary ice mass loss, which can be used to better assess the future contribution of the APIS to rising sea-levels.
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