Contrasting regional trends in interannual variability of Antarctic winter sea ice and their atmospheric teleconnections

Abstract

Previous studies have documented long-term changes in Antarctic sea ice extent and its interannual variability. However, spatial patterns of trends in the interannual variability of Antarctic sea ice concentration (SIC) and the mechanisms responsible for these changes remain poorly understood. Using satellite-derived SIC observations for 1979–2024 and a wavelet-based measure of interannual variance, we investigate changes in wintertime (July–September) SIC variability across the Southern Ocean. Significant decreases in interannual variance are identified in the Amundsen–Bellingshausen–Weddell Sea sector and the southeastern Indian Ocean–southwestern Pacific sector, whereas positive trends occur over much of the remaining Southern Ocean. EOF analysis reveals coherent modes of variability associated with these regional changes. The reduced SIC variability is linked to a decline in variability of convective activity over the southwestern tropical Pacific. Associated Rossby wave trains project onto a negative Southern Annular Mode-like circulation pattern, modulating the Amundsen Sea Low, surface winds, surface air temperature, and downward longwave radiation, thereby influencing Antarctic sea ice variability. In contrast, the apparent increase in SIC variability is largely driven by the exceptional Antarctic sea ice loss observed in 2023 during a mature El Niño event. Changes in the interannual variance of surface air temperature closely resemble those of SIC, whereas corresponding changes in sea surface temperature are weaker and regionally confined. These results provide new insights into the regional evolution of Antarctic sea ice variability and its links to tropical-extratropical climate teleconnections.