GLOBAL: New evidence of ice risk

Latest results from an international study of rock and sediment from the Antarctic sea floor show that only a small rise in atmospheric carbon dioxide concentrations could prompt significant, and potentially dangerous, changes to the West Antarctic ice.

Carbon dioxide is approaching 400 parts per million in the atmosphere and the new research, published in Nature magazine last week, shows that such a level of concentration enhances ice sheet melting caused by tilts in the earth's axis

The research is based on a 1,280 metre-long core from beneath the sea floor under the Ross Ice Shelf during the first project of the ANDRILL (ANtarctic geological DRILLing) research programme. The project involved more than 50 scientists from New Zealand, Italy, US and Germany, and refines previous findings about the relationship between atmospheric carbon dioxide concentration, ocean temperature, sea-level rise and natural cycles in Earth's orbit.

Professor Tim Naish, Director of Victoria University of Wellington's Antarctic Research Centre, and Professor Ross Powell from Northern Illinois University in the US are co-chief scientists of the project and, together with Dr Richard Levy from GNS Science and Professor Gary Wilson at Otago University, led publication of the new results on behalf of the project's international science team.

Naish says that based on ANDRILL data, combined with computer models of ice sheet behaviour, collapse of the entire West Antarctic Ice Sheet was likely to occur over about 1,000 years but recent studies show that melting has already begun.

A related study led by Dr David Pollard of Pennsylvania State University in the same issue of Nature reports results from a computer model. It shows that when the West Antarctic Ice Sheet collapsed, the margin of the East Antarctic Ice Sheet melted and global sea-level rose seven metres above present day levels.