Distinct atmospheric drivers of Ross Sea coastal polynya variability during winter

Abstract. Coastal polynyas in the Ross Sea have well-documented links to atmospheric circulation, but the role of specific circulation patterns in driving extreme wind events and their differential impact on individual polynyas remains poorly explored. This study examines peak-winter (Aug–Oct) variability in the Ross Sea, Terra Nova Bay, and McMurdo Sound polynyas using EOF analysis of high-resolution passive microwave sea-ice concentration data. Patterns of variability are related to surface extreme winds and 500 hPa geopotential height anomalies from ERA5, allowing concurrent assessment of local forcing and hemispheric-scale circulation connections.

Results reveal that each polynya responds differently to shifts in large-scale atmospheric features. Variations in the position and intensity of the Amundsen Sea Low, and its influence on Ross Ice Shelf Air Stream winds, are associated with marked changes in polynya area. By combining high-resolution sea ice concentration records with targeted extreme-wind analysis, this work identifies previously unresolved, location-specific atmospheric controls on Ross Sea polynya variability.