Abstract
Enhanced Antarctic ice sheet mass loss yields ocean surface freshening, cooling and sea ice expansion, which result in changes in the atmospheric conditions. Using the Southern Ocean Freshwater Input from Antarctica (SOFIA) multi‐model ensemble, we study the atmospheric response to a 100‐year idealized freshwater release of 0.1 Sv. All models simulate a surface‐intensified tropospheric cooling and lower‐stratospheric warming south of 35°S. Tropospheric cooling is attributed to sea ice expansion and the associated albedo enhancement in winter and a colder sea surface in summer. This cooling yields a downward displacement of the tropopause, reduced stratospheric water vapor content and ultimately warming around 200 hPa. An enhanced southward eddy heat flux explains warming at 10–100 hPa during austral winter. Despite a temporally (and spatially) uniform prescribed freshwater flux, a prominent sea ice seasonal cycle and atmosphere dynamics result in a distinct seasonal pattern in the occurrence and magnitude of the temperature responses.
Key Points:
· Tropospheric cooling and stratosphere warming south of 35°S are robust responses to Southern Ocean freshwater input in a multi‐model ensemble
· The tropospheric cooling is driven by enhanced surface albedo in winter and colder sea surface temperature in summer
· Two types of stratospheric warming, one caused by a lowering of the tropopause and reduced water vapor content in the lower stratosphere, another by an enhanced poleward eddy heat flux