Scientists from Edinburgh University discovered a basin the size of Wales close to the edge of the West Antarctic Ice Sheet which could affect how it moves.
The sub-glacial basin – nearly 1.2 miles deep in some places – was uncovered during radar mapping of the ice-covered landscape at the Weddell Sea.
Professor Martin Siegert, of the university, said: “This is a significant discovery in a region of Antarctica that 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 ice sheet behaves.”
The study was published in Nature Geoscience.