Pacific sub-decadal sea surface temperature variations contributed to recent Aantarctic Sea ice decline trend.

Total sea ice extent (SIE) across the Southern Ocean increased from 1979-2014, but declined rapidly after 2016. Significant sea ice decline has emerged since the peak of SIE in 2014, coincident with Pacific sub-decadal sea surface temperature (SST) trends resembling a strong La Niña-like cold condition and the negative phase of the interdecadal Pacific oscillation (IPO). Previous studies suggest that the warm subsurface Southern Ocean was an important driver of the low sea ice in spring 2016 and the sustained low sea ice state since. Here we show that the observed atmospheric circulation changes near Antarctica during the period from June 2013-May 2023 are conducive to increasing surface temperature via warm advection from north and reducing Antarctic SIE, involving a deepening of the Amundsen Sea Low and anomalous high pressures over the Weddell Sea and West Pacific sectors. Through coupled pacemaker experiments, we demonstrate that Pacific sub-decadal SST trends have dominantly driven these atmospheric circulation changes through tropical-polar teleconnections and also induced significant Southern Ocean subsurface warming in the recent decade. The consequent decreasing SIE has enhanced the Southern Ocean subsurface warming effect and significantly contributed to the rapid Antarctic SIE decline.