Calibrated sea level contribution from the Amundsen Sea sector, West Antarctica, under RCP8.5 and Paris 2C scenarios

Abstract. The Amundsen Sea region in Antarctica is a critical area for understanding future sea level rise due to its rapidly changing ice dynamics and significant contributions to global ice mass loss. Projections of sea level rise from this region are essential for anticipating the impacts on coastal communities and for developing adaptive strategies in response to climate change. Despite this region being the focus of intensive research over recent years, dynamic ice loss from West Antarctica and in particular from the glaciers of the Amundsen Sea represents a major source of uncertainty for global sea level rise projections. In this study, we use ice sheet model simulations to make sea level rise projections to the year 2100 and quantify the associated uncertainty using a comprehensive Bayesian approach aided by deep surrogates. The model is forced by climate and ocean model simulations for the RCP8.5 and Paris 2C scenarios, and it is carefully calibrated using measurements from the observational period. We find very similar sea level rise contributions of 19.0±2.2 and 18.9±2.7 mm by 2100 for Paris 2C and RCP8.5 scenarios, respectively. A subset of these simulations, extended to 2250, shows an increase in the rate of sea level rise contribution, and clearer differences emerge between scenarios, with increasing snow accumulation in RCP8.5 resulting in less cumulative mass loss. Our model simulations include both cliff-height- and hydrofracture-driven calving processes, and yet we find no evidence of the onset of rapid retreat that might be indicative of an unstable calving front retreat in any simulations within our modelled time frame.