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Abstract After a period of relative stability, the Antarctic sea ice extent has abruptly decreased in 2016 and has remained low since then. Both atmospheric and oceanic processes likely contributed to this drop but many questions remain regarding the underlying dynamics and it is unknown if this drop is unprecedented. Here we produce a new multi-variate spatial reconstruction covering 1958–2023 and show that a similar drop in sea ice extent occurred at the end of the 1970s, albeit with a smaller magnitude. Both drops show similar spatial patterns, with a higher sea ice loss in the East Antarctic sector than in the West Antarctic sector where the variability is strongly modulated by wind-driven changes. The ocean integrates the atmospheric forcing and provides memory that amplifies the magnitude of both drops.

Abstract Antarctic sea ice extent (SIE) reached a new record low in February 2023. Here we examine the evolution of the coupled ocean-atmosphere-sea ice system during the 12 months preceding the record. The impact of preceding conditions is assessed with observations, reanalyses, and output from the regional ocean-sea ice coupled model NEMO3.6-LIM3. We find that the 2022-2023 sea ice annual cycle was characterized by consistently low SIE throughout the year, anomalously rapid sea ice retreat in December 2022, and nearly circumpolar negative SIE anomalies in February 2023. While advection-induced positive air temperature anomalies inhibited the sea ice growth in most regions, strong southerly winds in the Amundsen-Ross Sea caused by an anomalously deep Amundsen Sea Low in spring transported notable volumes of sea ice northward, triggering an unusually active ice-albedo feedback onshore and favoring accelerated melt towards the minimum. This study highlights the impacts of multifactorial processes during the preceding seasons to explain the recent summer sea ice minima.

Positive phases of the Southern Annular Mode lead to enhanced basal melt overall in the Antarctic ice shelves, with strong losses in the Bellingshausen and Western Pacific sectors and gains in the Amundsen Sea, according to ice-ocean model experiments.