Record low Arctic sea ice extent in 2012 linked to two-year La Niña-driven sea surface temperature pattern

Arctic summer sea ice decline accelerated from the mid-2000s to 2012, with the 2012 record low remaining unbroken. While frequent La Niña events during this period have been suggested as a driver of this trend acceleration, no convincing evidence has been presented. Here, using a climate model nudged to observed pan-tropical sea surface temperatures (SST), we show that the back-to-back La Niña events during 2010–2011, followed by a North Pacific cooling and a marginal El Niño, were a key contribution to the 2012 record low. Specifically, the La Niña events in 2010–2011 warmed the Arctic Pacific sector, whereas tropical SST anomalies in 2012 strengthened the Greenland high pressure, leading to an Arctic dipole-like pressure pattern and strengthening of transpolar ice drift. These Arctic temperature and circulation anomalies led to the record low sea ice extent in 2012, highlighting the strong influence of tropical SSTs on Arctic climate.