An Abrupt Shift in the Arctic Ocean Warming due to Increased Extremes

Arctic sea ice has been shrinking since 1980s, and a sudden shift from thicker, deformed ice to thinner, more uniform ice occurred in 2007. The impacts remain unclear. Here we uncover a sudden 0.8°C rise and a doubling of sea surface temperature variability within the marginal ice zone (MIZ), pinpointing 2007 as a critical point of abrupt transition. Following a rapid expansion of the MIZ post-2007, Arctic marine heatwaves (MHWs) have intensified, accelerating sea ice melt and solar heat accumulation. Our analysis uncovers an intensified positive feedback between MHWs and Arctic Ocean warming. With continued greenhouse warming, destabilizing Arctic sea ice is expected to further intensify MHWs, exacerbating Arctic Ocean warming. Our findings underscore the critical role of climate extremes in triggering climate transitions.