Large-scale ice shelf calving events follow prolonged amplifications in flexure

The retreat of Antarctic ice shelves due to calving and the subsequent reduction in buttressing of the Antarctic Ice Sheet are of major concern for future sea-level rise. Sudden, widespread calving of weakened ice shelves has been linked to fracture amplification forced by ocean swell following regional sea-ice losses. Increases in magnitude and duration of swell-induced ice-shelf flexure in the lead-up to the calving events have not been tracked previously. We present seven-year datasets of sea-ice-barrier lengths and shelf-front flexural stress that encompass large-scale calving events of the Wilkins and Voyeykov ice shelves. We find the ice shelves share traits of preconditioning by prolonged amplifications in flexure and collapse of adjoining fast-ice barriers. We propose a conceptual model for the swell–sea-ice–shelf-front conditions leading to the calving events and discuss its implications further large-scale calving events as sea ice retreats and ice shelves thin.