Change in future climate due to Antarctic meltwater


Ben Bronselaer
Michael Winton
Stephen M. Griffies
William J. Hurlin
Keith B. Rodgers
Olga V. Sergienko
Ronald J. Stouffer
Joellen L. Russell


Meltwater from the Antarctic Ice Sheet is projected to cause up to one metre of sea-level rise by 2100 under the highest greenhouse gas concentration trajectory (RCP8.5) considered by the Intergovernmental Panel on Climate Change (IPCC). However, the effects of meltwater from the ice sheets and ice shelves of Antarctica are not included in the widely used CMIP5 climate models, which introduces bias into IPCC climate projections. Here we assess a large ensemble simulation of the CMIP5 model ‘GFDL ESM2M’ that accounts for RCP8.5-projected Antarctic Ice Sheet meltwater. We find that, relative to the standard RCP8.5 scenario, accounting for meltwater delays the exceedance of the maximum global-mean atmospheric warming targets of 1.5 and 2 degrees Celsius by more than a decade, enhances drying of the Southern Hemisphere and reduces drying of the Northern Hemisphere, increases the formation of Antarctic sea ice (consistent with recent observations of increasing Antarctic sea-ice area) and warms the subsurface ocean around the Antarctic coast. Moreover, the meltwater-induced subsurface ocean warming could lead to further ice-sheet and ice-shelf melting through a positive feedback mechanism, highlighting the importance of including meltwater effects in simulations of future climate.

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a, 2080–2100 meltwater-induced anomaly in the ocean temperature around the Antarctic coast at a depth of 400 m, relative to the standard ensemble. Hatching indicates where the anomalies are not significant at the 95% level. b, Time series of the ACT anomaly relative to the 1950–1970 mean. Lines as in Fig. 1.

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