Antarctica's icy origins

It takes 30 days to drill 700m of rock

Scientists in Antarctica have uncovered when the continent's vast ice sheets formed and are warning that they could melt as consequence of global warming.

Ancient rocks drilled from almost 1,000 metres below the sea floor contain climate data, as well as fossilised plants and micro-organisms. The scientists analysing the rocks are now confident that the formation of the ice sheets began between 33 and 34 million years ago - year zero for the frozen continent.

This could have implications for the future of the world's climate. Since the time when dinosaurs roamed a tropical Antarctic continent, the world has cooled down by 6.5 degrees Celsius.

That was 65 million years ago, but some scientists say that global warming could reverse this gradual cooling in as little as two or three centuries.

'Year zero'

"We are going to see a massive warming, there is no doubt about that," believes Mark Lavelle, of the British Antarctic Survey.

Lavelle believes global warming will lead to sea level rises

"And with that comes massive rises in sea levels. If we do finally get to year zero and see that the ice caps have finally disappeared, then the modellers tell us that we are looking at about a 70-metre increase in sea level. That changes the shape of the planet as we know it."

However, much of the recently-published research on Antarctic ice melting has presented a rather complex picture. Short-term satellite radar data has shown that the extent of the ice cover over the southern polar region is relatively stable, suggesting that any human-induced global warming that may be occurring has yet to have a major impact.

The West Antarctic Ice Sheet, a focus for concern because most of it is on land, is slowly melting, but the most recent data suggests it could be another 3,000 years at current rates before it disappears completely.

A clearer picture of ice melt may well come from a new Nasa satellite that is due to be launched in 2001.

Digging deep

The sedimentary rocks up to 350 million years old which are revealing Antarctica's past are being brought to the surface by the Cape Roberts Project.

The Cape Roberts drill rig floats on ice 20km offshore

At the south-west corner of the Ross Sea, a 57-tonne drill rig built on two metres of floating sea ice has been at work for the third year in succession.

The project is costing £4m and is an international collaboration. A number of boreholes have been drilled, up to a kilometre beneath the sea floor, itself up to 400m below the ice.

However, with the temperatures in early December beginning to rise for the Antarctic summer, the Cape Roberts project is preoccupied with a more immediate form of warming.

The ice which supports the drill rig is starting to weaken and melt, giving the team just a few weeks to drag all the equipment on it to the safety of the land.