Ancient channels preserved beneath the West Antarctic Ice Sheet suggest that part of the glacier prevailed during warm periods more than two million years ago.

By combining radio-echo soundings of the landscape underneath the glacier with satellite images of the ice surface, Kathryn Rose of the Bristol Glaciology Centre, UK, Martin Siegert at Imperial College London and their colleagues discovered a series of ancient wide, shallow channels. These suggest that, historically, there was a large flow of meltwater from the ice surface. The most recent period that was warm enough to generate such melting was during the Pliocene, 5.3 million to 2.6 million years ago.

Parts of this ice sheet, which some studies have predicted will destabilize in a warmer climate, may have existed at intervals during a period that was 2 °C warmer than now, the authors say.

Geology (2014)