Huge sub-glacial basin discovered under key Antarctic ice sheet could make it more unstable

A huge sub-glacial basin the size of Wales has been discovered under one of the key Antarctic ice sheets that could make it more unstable and liable to disintegration, a study has found.

Radar maps of the frozen Weddell Sea area of the West Antarctic Ice Sheet show that there is a deep sub-glacial basin measuring 100 km wide and 200 km long and up to 2 km deep on which the ice sheet appears to be floating.

Scientists fear that the area of the ice sheet that sticks out into the Weddell Sea, known as an ice "shelf", could melt away more quickly than previously supposed. This could cause the ice sheet itself to fall in to the sea, raising sea levels by several metres.

"We believe there's cause for concern....We believe this region is on the threshold of change," said Professor Martin Siegert of the University of Edinburgh, who led the project in conjuction with the British Antarctic Survey in Cambridge.

“This is a significant discovery in a region of Antarctica that at present we know little about. The area is on the brink of change, but it is impossible to predict what the impact of this change might be without further work enabling better understanding of how the West Antarctic Ice Sheet behaves,” Professor Siegert said.

The study, published in the journal Nature Geoscience, was designed to study the underlying landscape of the ice streams that feed the Filchner-Ronne Ice Shelf that acts as a kind of buffer for the ice sheet. The scientists found that there was a steep reverse slope with little in the way of "pinning points" that could delay the retreat of the ice sheet.

A separate study by a team of scientists from the Alfred Wegner Institute in Germany found that the ice shelf, which is currently melting at a rate of 5 metres a year, could be melting at up to 50 metres a year by the turn of the next century.

Jurgen Determann of the institute said: "Ice shelves are like corks in the bottles for the ice streams behind them. They reduce the ice flow because they lodge in bays everywhere and rest on islands. If, however, the ice shelves melt from below they become so thin the dragging surfaces become smaller and the ice behind them starts to move."