Why Antarctic Sea Ice Suddenly Collapsed After Decades of Growth

Antarctic sea ice had gradually expanded for decades, then dropped sharply in late 2015.

A cold ‘Winter Water’ layer beneath the ice had kept warmer deep water from reaching the ice from below.

Warming deep water thinned that Winter Water layer over time, reducing its protective effect.

Unusually strong winter storms in 2015 stirred the ocean, mixing warm deep water upward and melting ice from below.

A University of Gothenburg–led study published in Nature Climate Change links these processes and notes large year-to-year swings since 2015.