Heat wipes out giant Antarctic ice shelf

Nearly 300 square kilometres of a large ice shelf in Antarctica have disintegrated since October, caused by steadily warmer temperatures.

Nearly 300 square kilometres of a large ice shelf in Antarctica have disintegrated since October, caused by steadily warmer temperatures.

The Larsen B ice shelf on the east side of the Antarctic Peninsula could disintegrate further in weeks and even disappear, polar scientists believe. The shelf, marked on maps as a large bulge in the Weddell Sea, is now a bay, satellite photographs taken this month for the British Antarctic Survey show.

Scientists in Argentina worked out that Larsen B had lost 283 square kilometres - three-quarters of the size of the Isle of Wight - between 11 October and last Monday, a figure accepted by British and American experts.

Average temperatures on the peninsula, the northern tip of the continent which stretches towards the southern tip of South America, have risen by 2.5C in the past few decades, which researchers suspect is linked to global warming, although it cannot yet be proved. As a result, five ice shelves along the coast have disintegrated. The death of the Larsen A ice shelf, north of Larsen B, was spectacular. In a few days in January 1995, 1,300 square kilometres broke up.

"The collapse of these ice shelves is a remarkable indicator of climate change," said Dr Chris Doake, of the British Antarctic Survey. Ice shelves are floating extensions of the ice sheets covering Antarctic land. Warmth forms ponds of surface melt-water which seep down, hastening cracking of the ice.

The break-up does not imply rises in sea level, because the shelves are already displacing their own mass of water. But if the ice sheets over the continent itself were to break up and slide into the Southern Ocean, the world could face catastrophic sea-level rise.

Most scientists believe temperatures would have to rise very much more for that, although the ice sheet covering West Antarctica is believed to be potentially unstable. It is grounded on land which is below sea level, so water might seep under it and help its destruction if melting began.

A collapse of the west Antarctic ice sheet would raise world sea levels 12ft to 18ft, flooding regions across the world from East Anglia to Bangladesh. One expert put the chance of global warming causing that over the next two centuries at one in 1,000.