Quantifying 21st century Greenland ice mass loss from outlet glacier retreat and surface mass balance changes from coupled MAR-GISM simulations.

Mass loss from the Greenland Ice Sheet ice sheet has increased sixfold since the 1990s. With accelerated ice mass loss rates, it could become the largest contributor to sea-level rise in the 21^stcentury. Both the surface mass balance and outlet glacier retreat control this ice mass loss. The latter is decomposed between ice flow changes in the lower trunks of outlet glaciers (discharge) and calving of marine-terminating outlet glaciers. Partitioning between SMB and retreat contributors evolved through the last decade. It is uncertain how much they will contribute individually in the future. While a coupled RCM-ice sheet model helps to improve the SMB contribution, future glacier retreat contribution modelling is in its early stages. Using the RCM MAR, fully coupled to the GISM ice sheet model, we investigate the impact of the surrounding ocean on the outlet glaciers. Our parameterization, based on oceanic basins temperature and subglacial ice sheet runoff changes, simulates individual outlet glacier retreat rate. By forcing our atmosphere – GrIS – ocean-retreat-like model by several CMIP6 GCM models, we assess the 21^stcentury Greenland ice mass loss. Partitioning between mass loss from SMB and outlet glacier retreat forced by various CMIP6 SSP scenarios is estimated both at the regional and large Greenland scale.