Synoptic‐Scale Extreme Variability of Winter Antarctic Sea‐Ice Concentration and Its Link to Southern Ocean Extratropical Cyclones

Abstract

AbstractThis study provides a systematic analysis of extreme variability in winter Antarctic sea‐ice concentration (SIC) and its relationship with extratropical cyclones. We characterize sea‐ice variability and cyclone activity in different Southern Ocean sectors using atmospheric reanalyzes and a cyclone‐tracking algorithm, and then quantify the proportion of extreme sea‐ice variability engendered by cyclones of different intensities. The regions with relatively lower sea‐ice area (SIA) (the King Haakon VII, East Antarctic, and Bellingshausen sectors) have an even distribution of cyclones within all intensity ranges, while, in the sectors with higher SIA, the Ross/Amundsen displays a higher number of intense and weak cyclones, and the Weddell sector has the majority of weak cyclones. Our systematic analysis reveals a significant link between extreme variability in winter SIC and: (a) all cyclones in the Ross/Amundsen sector; (b) all but the weakest cyclones in the King Haakon VII, East Antarctic, and Bellingshausen sectors; and (c) all but the most intense cyclones in the Weddell sector. The latter result is explained by the fact that the Weddell sector experiences more frequent, weaker cyclones than the other sectors. Cumulatively, approximately 30%–40% of the extreme sea‐ice variability is caused by extratropical cyclones within all regions.