Antarctic sea ice response to meltwater due to Antarctic ice sheet mass loss in a multi-model ensemble

Abstract. We present the first multi-model study of the Antarctic sea ice response to enhanced meltwater due to dynamic mass loss from the Antarctic ice sheet. This meltwater flux (and its future increase under global warming) is not included in the most recent state-of-the-art climate model simulations used in CMIP6, representing a missing source of freshwater to the Southern Ocean. Previous climate model simulations have shown a wide range of responses in Antarctic sea ice and climate when this missing meltwater is introduced. Here, we analyze a new suite of 11 models comprising 43 ensemble members to assess the response to 0.1 Sv of Antarctic meltwater input at the ocean surface, evenly distributed around the Antarctic coastline under pre-industrial control forcing. Antarctic sea ice area increases in all models. However, there is a wide range in the response, with annual mean increases ranging from 0.71 to 4.14 million km². There is also substantial variation in both the spatial distribution and the time scale of the sea ice response. The intermodel spread in sea ice response is influenced by the model mean-state sea ice area and volume, the prevalence of open-ocean deep convection, and the mean-state stratification of the ocean. These findings highlight the importance of model mean-state biases in determining the response to a missing Antarctic meltwater boundary condition.