Scientists say melting of east Antarctic ice in climate change would raise sea levels by 60m

If the 4km-thick east Antarctic ice sheet melted due to climate change it would raise sea levels by 60 metres, and if that continent's much smaller western ice sheet disappeared like ice in a drink, the oceans would rise by up to six metres.

A group of experts on polar ice was quick to reassure, however, that this was unlikely, at least in our lifetimes. They were participants in what was described as the "Ice Breakers Session" yesterday during the British Association for the Advancement of Science annual conference this week in Sheffield.

Prof David Sugden, of the University of Edinburgh, pointed out that the eastern ice sheet had survived for 13 million years. It had endured warmer times three million years ago when hippopotami swam in rivers in what would become Britain and Ireland.

This ice sheet enjoyed a regional climate pattern that appeared untouched by the signs of global warming seen elsewhere.

The nearby western ice sheet and its floating ice shelves, for example, were gradually breaking up due to an increase in the local average temperatures.

This was not to say, however, that such a meltdown couldn't occur, he cautioned. Canada and the northern US carried a 34km thick dome of ice 14,000 years ago. A changed climate caused it to melt away in just 7,000 years, in the process raising sea levels by 100 metres.

The ice sheets lying across Greenland were also under some pressure and "unprecedented change" has been recorded in the key north Atlantic and Arctic ocean currents, said Dr Andrew Kerr, also of the University of Edinburgh.

Atlantic currents were what gave Ireland, Britain and much of western Europe their temperate climate, and altered currents could be indicators of a very cold future. All of these areas were under deep glaciers just 10,000 years ago. Many of the significant changes noted over the past decade related to alterations to the "fresh water balance", he said.

North Atlantic currents were driven by a complex and only vaguely understood interaction between temperature gradients, sea salinity and the inflow of fresh water from rain, snow and glacier melt over the land.

Dr David Vaughan, of the British Antarctic Survey, discussed the retreat of the massive ice shelves that projected over the seas west of the Antarctic continent. "Over the past few years that retreat has accelerated," he said.

Dr Julian Dowdswell, of the University of Bristol, described a few of the bad effects, aside from rising sea level, that could come from the decline of polar ice caps.

There was evidence that retreating glaciers and ice shelves over the north Atlantic dumped tremendous amounts of unstable rubble on to the sea floor, including at the continental slope where relatively shallow waters dropped off into the deep ocean.

A piece of the slope gave way about 7,000 years ago in a huge underwater landslide that in turn triggered an enormous tsunami or wave that swamped European coastlines. The break-up of polar ice sheets and shelves would also greatly increase the creation of icebergs that could drift off into important sea lanes.