Conditions leading to the unprecedented low Antarctic sea ice extent during the 2016 austral spring season

The 2016 austral spring was characterized by the lowest Southern Hemisphere (SH) sea ice extent seen in the satellite record (1979 to present) and coincided with anomalously warm surface waters surrounding most of Antarctica. We show that two distinct processes contributed to this event: First, the extreme El Niño event peaking in December–February 2015/2016 contributed to pronounced extratropical SH sea surface temperature and sea ice extent anomalies in the eastern Ross, Amundsen, and Bellingshausen Seas that persisted in part until the following 2016 austral spring. Second, internal unforced atmospheric variability of the Southern Annular Mode promoted the exceptional low sea ice extent in November–December 2016. These results suggest that a combination of tropically forced and internal SH atmospheric variability contributed to the unprecedented sea ice decline during the 2016 austral spring, on top of a background of slow changes expected from greenhouse gas and ozone forcing. Key Points Record low Antarctic sea ice extent in 2016 austral spring can be related to two rare events First: anomalously long quasi‐stationary persistence of El Niño‐induced SST anomalies in the eastern Ross, Amundsen, and Bellingshausen Seas Second: unforced SAM variability driving warm SSTs and sea ice decline in most of the remaining Southern Ocean sectors