Atmosphere and ocean climate model resolution in resolving Weddell Sea polynyas and their ocean-atmosphere interactions.

The Weddell Sea Polynya is a seasonal opening within the sea ice cover of the Weddell Sea sector, typically found over the Maud Rise and inside the Weddell Gyre. It has been a rare occurrence in the satellite period, appearing in austral spring between 1973 and 1976 and again in 2016/17. The polynya formation has been shown to be complex, requiring a combination of ocean and atmospheric mechanisms to develop. The region is often poorly resolved in global climate models, with little agreement in ocean or sea ice dynamics. When Weddell Sea polynyas have occurred in models without forcing, it is not understood how they occur within the model, or why some models produce frequent polynyas and others produce none. Some studies have shown that increasing horizontal resolution improves the dynamics of the Southern Ocean, allowing for better parameterisation of small-scale features. Here, we use multi-model data of different resolutions, from the PRIMAVERA HighResMIP experiments, to determine how models of different atmospheric and ocean resolution resolve Weddell Sea polynyas. We assess the frequency, size, and location of polynyas in different resolutions, in addition to studying the ocean and atmospheric processes associated with the polynya in these models. Initial results of models that resolve frequent polynya show preconditioning in both the ocean and atmosphere, in addition to a small response to the polynya in the months following.