The key role of the Southern Annular Mode during the sea-ice maximum for Antarctic sea ice and its recent loss.

Antarctic sea ice exhibits considerable interannual variability and has experienced unprecedented decline over the past decade. Here we provide observational insights into the role of the Southern Annular Mode in driving such variations in Antarctic sea-ice area. The influence of the Southern Annular Mode on Antarctic sea-ice area exhibits more pronounced seasonality than indicated in previous work. Positive anomalies in the Southern Annular Mode lead to decreases in sea-ice area during the seasonal sea-ice maximum, but vice versa during the sea-ice minimum. Variations in Southern Annular Mode during the sea-ice maximum also have an outsized influence on annual-mean changes in sea-ice area, since the seasonally-varying persistence and shortwave effects of sea-ice anomalies peak during the following months. It is argued that a notable fraction of the dramatic losses in annual-mean sea-ice area over the past decade can be traced to variations in the Southern Annular Mode during the sea-ice maximum.