A drop in Antarctic sea ice extent at the end of the 1970s

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. Antarctic sea ice extent decreased abruptly in 2016 and has remained low since then, with similar drops in the 1970s but smaller magnitude, in which the higher sea ice loss occurred in the East Antarctic sector due to ocean atmospheric forcing, according to results from a multi-variate spatial reconstruction from 1958 to 2023.