Combined influences of Atmospheric precursors on Antarctic sea ice and its record low in February 2023

This study investigates the impact of major climatic modes on the interannual variability of the annual minimum extent of Antarctic sea ice. It shows that the Southern Annular Mode (SAM), the Indian Ocean Dipole (IOD) and the El Niño-Southern Oscillation (ENSO), along with the total sea ice condition during the preceding spring serve as precursor signals of February sea ice extent (SIE). These climate modes interact, energizing the Pacific-South American pattern (PSA), which deepens and shifts the Amundsen Sea Low (ASL) westward in spring. This generates a dipole sea ice anomaly characterized by increased sea ice in the northern Ross Sea but decreased ice in the Bellingshausen and northern Weddell Seas. However, as the season transitions into summer, the ASL exerts a pronounced delayed effect, contributing to widespread sea ice loss across west Antarctica. Strong southerly winds on the western flank of the ASL push sea ice away from the inner Ross Sea, exposing coastal waters that absorb solar radiation, accelerating ice melt through positive ice-albedo feedback. Simultaneously, northwesterly winds on the eastern flank transport warm air toward the Bellingshausen and northern Weddell Seas, intensifying ice loss in these regions. Furthermore, the active PSA is accompanied by a tripole sea surface temperature pattern, featuring warming in the Weddell Sea that promotes continued ice melt. The co-occurrence of an exceptionally positive SAM, a La Niña, and a strong negative IOD during the spring 2022, combined with lower-than-normal total spring SIE, ultimately contributed to the record-low Antarctic SIE observed in February 2023.