Ocean Warming Triggered Widespread 2015 Antarctic Sea Ice Loss

Nature Climate Change, 18 March 2026

Sea ice extent around Antarctica was fairly stable or very slightly (1-2%) expanding for several decades until reaching record-breaking lows in 2017, when strong winds churned up warm water from the deep ocean, breaking through the “winter water” layer that previously protected the ice from melting. Antarctic winter water insulates sea ice from warm circumpolar deep waters from the tropics that ring the continent. Two decades of measurements now show that Antarctic winter water has thinned over large parts of the Southern Ocean. When strong storms in 2015 stirred up the sea and mixed warmer deep water with this cold-water layer, the protection disappeared and sea ice melted at record speed. Antarctic sea ice has not recovered since. While anomalous winds drove the 2015 record-breaking low, the sustained lack of sea ice since that point indicates that winter water remains too thin to prevent deep waters from billowing up against the ice. This regime shift poses a serious risk to polar species, including krill that rely on stable sea ice, and threatens the future stability of Antarctic ice shelves. It could also impact global ocean currents, including the important Atlantic Meridional Overturning Circulation (AMOC), carrying broader implications for global climate and weather.

Paper | Summary by the University of Gothenburg | News Coverage