Contrasting the Impact of Arctic and Antarctic Stratospheric Sudden Warmings

Stratospheric sudden warmings (SSWs) represent powerful disturbances of the wintertime polar vortex. They are a form of internally generated variability, related to upward propagating planetary waves that perturb the vortex. SSWs have substantial impacts on the intraseasonal to interannual variability of the extratropical atmosphere all the way down to the surface. This includes potential changes in ocean circulation and sea ice coverage. SSWs are much more common over the Arctic than over the Antarctic. The shortness of the observational record raises the questions of how frequent SSW events actually are and how the basic meteorology of SSWs differs between the two hemispheres. Here, we use an 8000 year-long control integration with a stratospherically-enhanced version of the GFDL climate model CM2.1 to answer our questions. The long integration allows us to provide, for the first time, a realistic estimate of how often SSWs occur over the two poles. We evaluate the impact of SSWs at the surface and how they differ between the two hemispheres. A particular emphasis is placed on understanding the role of SSWs for the distribution of sea ice.