Sea Ice: Last Line of Defense for Weakened Antarctic Ice Shelves

Nature Geoscience, 1 July 2025

Researchers tracking sea ice, ocean swell and ice shelf conditions over multiple years in two sectors of Antarctica have identified key triggers and common patterns of large-scale Antarctic ice shelf calving events. Floating slurries of sea ice protect the margins of ice shelves from incoming ocean waves, which can strike with enough force over time to bend and break away large portions of the ice into the ocean. The study documented how prolonged periods with reduced sea ice (on the scale of 6-18 months) occurred prior to three major ice shelf calving events. In final weeks before collapse, each of these ice shelves lost the residual band of sea ice attached to their outer edge, a warning sign of major ice loss soon to occur. Antarctic sea ice is a critical factor for ice shelf stability. If this protective sea ice barrier disappears for extended periods of time, the force of ocean waves hitting exposed shelf ice seems to be more important than even potentially extreme rates of ice shelf thinning from warmer surface or ocean temperatures.

Full Paper | Nature Research Briefing | News Coverage from the University of Melbourne