The floating ice shelves along the seaboard of the Antarctic ice sheet restrain the outflow of upstream grounded ice1, 2. Removal of these ice shelves, as shown by past ice-shelf recession and break-up, accelerates the outflow3, 4, which adds to sea-level rise. A key question in predicting future outflow is to quantify the extent of calving that might precondition other dynamic consequences and lead to loss of ice-shelf restraint.

Reliable forecasts of sea-level rise depend on accurately modelling the dynamics of polar ice sheets. A numerical framework that better reflects ice-sheet basal drag adds greater realism to such models.