Barystatic sea-level changes are geographically variable due to solid Earth gravitational, rotational and deformational (GRD) effects and feed back onto dynamics of the marine-based West Antarctic Ice Sheet (WAIS), whose stability is a main source of uncertainties in projections of the Antarctic Ice Sheet. While it is common in paleo ice-sheet modeling applications to capture GRD, the majority of ice-sheet models applied to predict future changes omit these effects because of the shorter (decadal to centennial) timescale of their projections.
In this presentation, we show our work on coupling the higher-order, three-dimensional MPAS-Albany Land Ice (MALI) model to a 1D global sea-level model that captures GRD effects. In particular, we assess the impact of regional sea-level changes due to GRD effects on the Antarctic Ice Sheet evolution under the ISMIP6-AIS-2300 protocol. Compared to standalone ice-sheet simulations that use fixed bed topography, the coupled ice sheet-sea level simulations show multi-decadal to centennial-scale delays in the retreat of Thwaites Glacier in West Antarctica, confirming the “stabilizing” effects of GRD feedback. Our results further show decreased delay in the retreat of the WAIS with increased strength of the applied climate forcing, implying the pertinence of our commitment to limiting greenhouse gas emissions. In addition, we investigate the differences in the global mean sea-level change calculated based on the same ice mass loss scenario, but separately by the ice-sheet model corrected for bedrock changes (Goelzer et al. 2020) and by the global sea-level model. We first describe details of domain definitions and remapping necessary to ensure conservation between planar ice-sheet and spherical sea-level grids. We also highlight the differences between the two methods of calculating global mean sea level due to processes included in the global sea-level model but not representable in ice-sheet models or corrections to them. Overall, our results demonstrate the importance of including GRD effects in future ice-sheet projections and of being explicit in calculation of global mean sea-level change when communicating ice-sheet mass loss in terms of sea level.