Causes of the record-low Antarctic sea-ice in austral summer 2022

The Antarctic sea-ice area reached a record minimum during austral summer 2022 (December 2021 to February 2022), with particularly considerable loss in the West Antarctic. Based on lead–lag correlation analysis, the authors found that the record minimum was closely linked to the preceding near-strongest positive-phase Southern Annular Mode during August–October 2021 and stronger positive SST anomaly in the Maritime Continent during July–September 2021. The former remained at a historically near-strongest or strongest level because of the stratospheric cooling effect of the unprecedented stratospheric ozone depletion, which induced a deepened and southwestward-shifted Amundsen Sea Low (ASL), causing sea-ice retreat via horizontal wind anomalies. The latter persisted into summer and favored the development of La Niña, which generated deep convection over the southwestern subtropical Pacific and triggered a southeastward-propagated Rossby wave train, deepening the ASL remotely. The ozone reduction also induced surface warming in the West Antarctic by increasing the net downward shortwave radiation, thereby intensifying the sea-ice loss. Additionally, positive feedback between the SST, net shortwave radiation and cloudiness, along with the Ekman heat transport, amplified the surface warming.