Identifying the Antarctic melt contribution to Last Interglacial sea level from Eurasian relative sea-level records

Oliver Pollard , Natasha Barlow, Lauren J Gregoire, Natalya Gomez, Lachlan C. Astfalck , Amy McGuire

High global mean sea level during the Last Interglacial was likely to have largely been driven by Greenland and Antarctic melt, but the timings, rates, and relative magnitudes of these contributions remain elusive. Due to the geometry of ice-sheet fingerprints, relative sea level records in the Eurasian region are likely to be sensitive to ice mass changes in Antarctica while being relatively insensitive to changes in Greenland, making them ideal targets for identifying scenarios of past Last Interglacial ice-sheet melt. We produce an ensemble of Eurasian relative sea level models, driven by regional glacial-isostatic adjustment due to the penultimate glacial cycle, and a systematic suite of Antarctic melt scenarios in order to compare our simulations against Last Interglacial relative sea level records from the WALIS sea level database. By performing regional sensitivity analysis, we identify Eurasian data regions most sensitive to Antarctic ice sheet melt. Through the use of a bespoke Bayesian history matching framework, we uncover glacial isostatic adjustment and Antarctic ice sheet melt scenarios that most closely match regional relative sea level data within uncertainty. Our results show that data points off the coast of Wales, northwest France, and the English Channel are most sensitive to Antarctic melt but that all modelled relative sea level scenarios are able to fit the suite of relative sea level data within 3-sigma uncertainty. Despite this, by utilising relative sea level data that we have identified as strongly sensitive to Antarctic ice-sheet changes, our data-model analysis reveals a clear preference for high magnitudes of total melt, identifying an Antarctic contribution of between 3.2 - 9.3 m to the Last Interglacial global mean sea level highstand (likely, 66th percentile).