Drivers of Spatially Heterogeneous Changes in Summertime Sea Ice Variability in the Weddell Sea

Abstract. Interannual variability of Antarctic sea ice has undergone substantial changes in recent decades, particularly in the Weddell Sea. Previous study examined the change in interannual variability of sea ice extent (SIE) in the Weddell Sea. However, the spatial characteristics and driving mechanisms of changes in sea-ice concentration (SIC) interannual variability within the Weddell Sea remain insufficiently understood. Here, we investigate changes in austral summer (January–March) interannual SIC variability in the Weddell Sea during 1979–2024. The results reveal a distinct dipole pattern, characterized by increasing interannual variability in the northern Weddell Sea and decreasing variability in the southern Weddell Sea. Enhanced convective activity over eastern Australia and the southern Indian Ocean excites separate Rossby wave trains that propagate into the Southern Ocean and generate opposite zonal pressure gradients over the Weddell Sea. The resulting anomalous northerly (southerly) winds promote sea ice convergence and increased sea-ice concentration in the southern (northern) Weddell Sea, thereby contributing to reduced (enhanced) interannual sea-ice variability.