Antarctica's vast ice sheets may be more vulnerable to warming than was thought.

Using a three-dimensional computer model, David Pollard of Pennsylvania State University in University Park and his colleagues identified two new ways in which ice sheets can collapse. Meltwater and rainfall can drain into crevasses in the ice, leading to vertical fractures. Moreover, heavy ice near the top of the sheets can break apart, shearing off huge chunks.

The results may help to explain how the East Antarctic Ice Sheet could have collapsed enough to cause the high sea levels that occurred during warm periods over the past 25 million years. Accounting for these mechanisms, the authors suggest that the West Antarctic Ice Sheet could collapse faster than predicted — over decades rather than centuries to millennia.

Earth Planet. Sci. Lett. 412, 112–121 (2015)