Abstract Antarctic sea ice has recently shifted to a new low-extent regime, yet the underlying mechanisms remain uncertain. This study reveals an interdecadal shift in the spring Southern Annular Mode (SAM) pattern around 1998, after which its lagged influence on summer Antarctic sea ice intensified, particularly in the Weddell and Ross Seas. After 1998, the SAM exhibits stronger wave-like structures, featuring an intensified Pacific–South American (PSA)-like pattern that drives regional sea-ice loss. In the Weddell Sea, the positive SAM‑related anticyclonic circulation induces upper-ocean warming that promotes summer ice melt. However, in the Ross Sea, a deepened Amundsen Sea low enhances offshore ice export and positive ice‑albedo feedback, increasing summer ice loss. This interdecadal SAM shift is likely modulated by tropical variability, as the increased co-occurrence of a positive SAM with La Niña strengthens PSA-mediated processes. These findings highlight the nonstationary nature of tropical–polar linkages in recent Antarctic sea-ice lows.
Dou et al. (2026) studied this question.