| Summary: | Recent trends in Southern Ocean (SO) climate—of surface cooling, freshening, and sea ice expansion—are not captured in historical climate simulations. Here we demonstrate that the addition of a plausible increase in Antarctic meltwater to a coupled climate model can produce a closer match to a wide range of climate trends. We use an ensemble of simulations of the Goddard Institute for Space Studies Earth system model to compute “climate response functions” (CRFs) for the addition of meltwater. These imply a cooling and freshening of the SO, an expansion of sea ice, and an increase in steric height, all consistent with observations since 1992. The CRF framework allows one to compare the efficacy of Antarctic meltwater as a driver of SO climate trends, relative to greenhouse gas and surface wind forcing. The meltwater CRFs presented here strongly suggest that interactive Antarctic ice melt should be included in climate models.
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