Regional extreme Antarctic sea-ice retreat linked to tropical forcing

While previous studies have focused on monthly-to-decadal drivers of recent Antarctic sea-ice change, the role of short-lived extreme events remains unclear. Here we investigate extreme Antarctic sea-ice reduction events over 1979–2022 using observations and reanalyses, focusing on the warm sea-ice retreat season (September to February). We find these extreme events generally last only 2 days, but each contributes about 5% of each sector’s total seasonal sea-ice decline, with a cumulative contribution reaching 41% of the total circumpolar seasonal retreat. Sea-ice loss during these events is dominated by thermodynamic melting linked to surface heat flux anomalies. In the Ross-Amundsen, Amundsen-Bellingshausen, and Weddell Seas, extreme sea-ice reductions are tied to high-latitude blocking events triggered by deep convection over the Maritime Continent and central tropical Pacific. The convection excites stationary Rossby waves, generating blocking to the east of the extreme retreat that transports heat and moisture poleward via atmospheric rivers. In contrast, extreme reduction events in the Indian Ocean sectors are caused by anomalously strong cyclones governed by internal mid-latitude synoptic-scale wave activity. Short-lived extreme reduction events of Antarctic sea ice cumulatively contribute to 41% of the total seasonal ice retreat, and some of the events are remotely triggered by deep convection over the tropics, revealed by analysis based on reanalysis data.