Rapid Thinning of Floating Ice Debris Threatens Ice Shelf Stability in Antarctica

Proceedings of the National Academy of Sciences, August 5

A major pre-existing crack in the Larsen C Ice Shelf broke open in 2017, releasing one of the largest Antarctic icebergs on record. The “ice mélange” – a stabilizing mixture of sea ice, iceberg debris, and snow – surrounding the ice shelf had formerly provided enough support to prevent this crack from completely splitting. However, this study found that the circulation of warm waters underneath the ice shelf, in combination with warm winds blowing across its surface, accelerated the melting of the mélange. Without this external support, the Larsen C Ice Shelf completely cracked and released an iceberg four times the size of London. Such ice mélanges serve as the glue that holds together large segments of floating ice shelves. Current models assume that ice shelves are at risk only if melt water ponding occurs. This study reveals the critical importance of ice mélanges on ice shelf stability. Rising global temperatures weaken these stabilizing ice mixtures, preventing them from healing the cracks in Antarctic ice shelves and thus carrying the potential for faster and greater future sea level rise.

https://www.pnas.org/content/118/40/e2105080118