Antarctic Peninsula ice shelf collapse triggered by föhn wind-induced melt

Abstract. Ice shelf collapse reduces buttressing and enables glaciers to contribute more rapidly to sea-level rise in a warming climate. The abrupt collapses of the Larsen A and B ice shelves on the Antarctic Peninsula (AP) have been attributed to increased surface melt. However, no studies examine the timing, magnitude, and location of surface melt processes immediately preceding these disintegrations. Here we use a regional climate model and Machine Learning analyses to evaluate the influence of föhn wind events on the surface liquid water budget for collapsed and extant ice shelves. We find föhn winds caused 25 % of the total annual melt in just 9 days on Larsen A which helped melt lakes surpass a critical stability depth that, we suggest, ultimately triggered collapse. By contrast, föhns appear to pre-condition, not trigger, Larsen B's collapse. AP extant ice shelves will remain less vulnerable to surface-melt-driven instability due to weaker föhn-driven melt so long as surface temperatures and föhn occurrence remain within historical bounds.

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