The influence of present-day regional surface mass balance uncertainties on the future evolution of the Antarctic Ice Sheet.

Rising global sea levels are one of many impacts, the current anthropogenic global warming poses to humanity. The Antarctic Ice Sheet (AIS) has the potential to contribute several meters of sea level rise over the next few centuries. To predict future sea level rise contributions from ice sheets, both global and regional climate model (RCM) outputs are used as forcing in ice sheet model simulations. While the impact of different global models on future projections is well-studied, the impact of different regional models on the evolution of the AIS is not well-constrained. In our study, we investigated the impact of the choice of present-day reference RCM forcing on the evolution of the AIS. We used the Parallel Ice Sheet Model (PISM) to study the AIS in a constant forcing quasi-equilibrium state and under future projection s, combining present-day RCM output with global climate model projections. Our study shows that the choice of RCM reference forcing results in uncertainties of future sea level rise predictions of 8.7 (7.3–9.5) cm in the year 2100 and 24.3 (16.3–46.5) cm in 2300 under the RCP8.5 scenario. Those uncertainties are of the same order of magnitude as the choice of the underlying ice sheet model parameterization and global climate model. Additionally, our study shows that the choice of RCM reference affects the extent of grounding line retreat in West Antarctica in future projections and can result in the potential long-term collapse of the West Antarctic Ice Sheet in quasi-equilibrium simulations. Our study therefore highlights the importance, of a careful choice of RCM reference forcing for simulations of the AIS. [ABSTRACT FROM AUTHOR]