Model Assessment of Winter Extratropical Cyclone Short-Term Impacts on the Antarctic Marginal Ice Zone

Abstract. The Antarctic marginal ice zone (MIZ) is the transitional region between the Antarctic sea ice edge and the consolidated ice cover, which is characterised by the presence of ocean surface waves and relatively small ice floes, and is a region where atmospheric and oceanic processes strongly influence sea ice dynamics. Extratropical polar cyclones intensify these processes by amplifying wave activity, transporting heat and moisture, and driving sea ice drift across the MIZ. Here, the CICE sea ice model with a wave propagation module is used at a 0.25° resolution to analyse statistically the impact of ∼400 cyclones on the location of the Antarctic ice edge and MIZ width. Cyclone-driven winds cause sudden shifts of ∼20 km in the ice edge location, through both compaction and expansion, with expansion events more effective in early winter and compaction later. MIZ widening is primarily driven by short-lived, major wave-induced breakup events, which increase the MIZ width by ∼30 km on average, with greater breakup associated with greater widening. Extreme ice edge changes result from the combined influence of sea ice drift and thermodynamics, whereas extreme MIZ width changes are primarily governed by the presence or absence of wave activity. These findings highlight the varied yet pronounced responses of the Antarctic MIZ to extratropical cyclones and underscore the critical role of waves in shaping the boundary between the MIZ and the consolidated ice pack, reinforcing the need to account for wave impacts in future studies.