ISMIP6 Antarctica: A multi-model ensemble of the Antarctic ice sheet evolution over the 21st century
Seroussi, H and Nowicki, S and Payne, AJ and Goelzer, H and Lipscomb, WH and Abe-Ouchi, A and Agosta, C and Albrecht, T and Asay-Davis, X and Barthel, A and Calov, R and Cullather, R and Dumas, C and Galton-Fenzi, BK and Gladstone, R and Golledge, NR and Gregory, JM and Greve, R and Hattermann, T and Hoffman, MJ and Humbert, A and Huybrechts, P and Jourdain, NC and Kleiner, T and Larour, E and Leguy, GR and Lowry, DP and Little, CM and Morlighem, M and Pattyn, F and Pelle, T and Price, SF and Quiquet, A and Reese, R and Schlegel, NJ and Shepherd, A and Simon, E and Smith, RS and Straneo, F and Sun, S and Trusel, LD and Breedam, JV and Van De Wal, RSW and Winkelmann, R and Zhao, Chen and Zhang, T and Zwinger, T, ISMIP6 Antarctica: A multi-model ensemble of the Antarctic ice sheet evolution over the 21st century, Cryosphere, 14, (9) pp. 3033-3070. ISSN 1994-0416 (2020) [Refereed Article]
Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to different climate scenarios and assess the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimates of the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes, forcings employed and initial states of ice sheet models. This study presents results from ice flow model simulations from 13 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015-2100 as part of the Ice Sheet Model Intercomparison for CMIP6 (ISMIP6). They are forced with outputs from a subset of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), representative of the spread in climate model results. Simulations of the Antarctic ice sheet contribution to sea level rise in response to increased warming during this period varies between 7:8 and 30.0 cm of sea level equivalent (SLE) under Representative Concentration Pathway (RCP) 8.5 scenario forcing. These numbers are relative to a control experiment with constant climate conditions and should therefore be added to the mass loss contribution under climate conditions similar to presentday conditions over the same period. The simulated evolution of the West Antarctic ice sheet varies widely among models, with an overall mass loss, up to 18.0 cm SLE, in response to changes in oceanic conditions. East Antarctica mass change varies between 6:1 and 8.3 cm SLE in the simulations, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional simulated mass loss of 28mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the climate forcing, the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 climate models show an additional mass loss of 0 and 3 cm of SLE on average compared to simulations done under present-day conditions for the two CMIP5 forcings used and display limited mass gain in East Antarctica.
ISMIP6 Antarctica, Antarctic ice sheet evolution over the 21st century, ice sheet modelling