J. Glaciol. 60, 205–214 (2014)

Approximately 20% of Antarctic ice shelves have collapsed since the 1970s, with hydrofracturing — where water enters through tiny crevasses and pushes the ice apart — thought to be the cause.

Peter Kuipers Munneke, of Utrecht University, the Netherlands, and co-workers use a firn (an ice–air matrix of partly compacted snow) model to study the long-term processes leading to iceshelf collapse. Increased temperatures are increasing surface melt and thus water is available to enter the firn at the ice surface, where it refreezes. This process does not weaken the iceshelf. However, once all of the air has been displaced by the refrozen meltwater over a number of years, the iceshelf is susceptible to water entering and causing hydrofracturing, and ultimately collapse.

Firn air depletion is found to be a top requirement for hydrofracturing but it does not necessarily indicate that a collapse will occur. Climate-model projections suggest many more iceshelves could collapse in the next 200 years, however some could be protected by increased snowfall.