Sensitivity experiments for the Antarctic ice sheet with varied sub-ice-shelf melting rates

Ice-sheet modelling is an important tool for predicting the possible response of ice sheets to climate change in the past and future. An established ice-sheet model is SICOPOLIS (Simulation COde for POLythermal Ice Sheets), and for this study the previously grounded-ice-only model was complemented by an ice-shelf module. The new version of SICOPOLIS is applied to the Antarctic ice sheet, driven by standard forcings defined by the SeaRISE (Sea-level Response to Ice Sheet Evolution) community effort. A crucial point for simulations into the future is to obtain reasonable initial conditions by a palaeoclimatic spin-up, which we carry out over 125 000 years from the Eemian until today. We then carry out a set of experiments for 500 years into the future, in which the surface temperature and precipitation are kept at their present-day distributions, while sub-ice-shelf melting rates between 0 and 200 m a(-1) are applied. These simulations show a significant, but not catastrophic, sensitivity of the ice sheet. Grounded-ice volumes decrease with increasing melting rates, and the spread of the results from the zero to the maximum melting case is similar to 0.65 m s.l.e. (metres sea-level equivalent) after 100 years and similar to 2.25 m s.l.e. after 500 years.