Pictures from the European Space Agency's Envisat satellite have shown how waves created by the Japanese tsunami in March broke chunks off an Antarctic ice shelf.

The waves, which travelled halfway across the world to reach the Antarctic, would very likely have been only 30cm high.

But the stress caused by a series of such waves was enough to weaken the Sulzberger Ice Shelf, which has been stable for 46 years, causing 125 sq km of ice to break off.