Antarctic Ice Sheet – Climate Feedbacks Under High Future Carbon Emissions

Observational evidence indicates that the Antarctic Ice Sheet (AIS) is losing mass at an accelerated rate while ice sheet models highlight the potential for a significant ice collapse over the next few centuries. Freshwater forcing from a retreating AIS could have a variety of impacts on the climate system, leading to both positive and negative feedbacks on anthropogenic warming. Here, we present projected changes to the climate system over the next 250 years from a fully coupled global climate model (CESM 1.2) run under future greenhouse gas emissions scenarios IPCC RCP4.5 and 8.5 with meltwater discharge provided by a dynamic-thermodynamic Antarctic Ice Sheet model. Accounting for Antarctica’s meltwater contribution raises sub-surface ocean temperatures at the ice sheet margin by more than 1ºC, with the potential to substantially increase ice shelf basal melt rates beyond those currently projected. In contrast, a strong cooling of both the surface air and ocean temperatures results in an extensive expansion of perennial sea-ice in the Southern Ocean. Accounting for Antarctic meltwater delays the increase in anthropogenic warming, the onset of ice-free conditions in the Arctic, and the projected weakening of the Atlantic Meridional Overturning Circulation (AMOC). Our results demonstrate a clear need to more accurately account for meltwater input from ice sheets if we are to make confident climate predictions.