Polar bears' habitat threatened by thinning of Arctic sea ice

The main natural habitat of the polar bear is under increasing threat as a consequence of the dramatic thinning of the Arctic sea ice.

The link between the thinning of the ice and rising temperatures has been discovered by scientists at UCL and the Met Office Hadley Centre for Climate Prediction and Research, whose findings are due to be published in the 30th October edition of Nature.

The thinness of the ice covering the Arctic Ocean, approximately three metres deep, makes it far more vulnerable to longer summers than the glaciers of the Antarctic. A 40% thinning of the ice has occurred since the 1960s. Polar bears rely on the ice to hunt for seals, and its earlier break-up is giving them less time to hunt. Continued decrease in the Arctic's ice cover would also act to increase the effects of global warming in the northern hemisphere by decreasing the amount of sunlight reflected by the ice. It is also believed that the Arctic ice plays a role in the operation of the Gulf Stream, and that this could be disrupted by continued thinning.

Previous studies suggesting that the decrease in ice cover was caused by changing wind patterns relied on computer models to arrive at their conclusions. The new results are based upon observation and measurements made possible by the use, for the first time, of radar data from a European Space Agency satellite and microwave images obtained from an American satellite, to determine changes in the length of the Arctic summer.

Dr Seymour Laxon, from the Centre for Polar Observation and Modelling at UCL, said: "Results from the American satellite have shown that the length of summers has increased over the last 25 years. When we compared the data from the two satellites we were astonished by the similarity between changes in the ice thickness and the length of the summer melt season. This result suggests that if this continues, further melting will occur, leading to the eventual disappearance of the ice during summer."

Notes to editors:

1. "High interannual variability of sea ice thickness in the Arctic region," by Seymour Laxon (UCL), Neil Peacock (UCL) and Doug Smith (Met Office Hadley Centre for Climate Prediction and Research), will be published in the 30th October edition of Nature. The research was funded by the Natural Environment Research Council (NERC) and the European Union.
2. For further information, photographs or other graphics illustrating the phenomenon, or to interview Dr Laxon, contact Dominique Fourniol in the UCL media relations office on 0207 679 9728 or d.fourniol@ucl.ac.uk
3. The impact on sea levels of the melting of the Arctic ice is minimal, and should not be confused with the issue of global warming melting the glaciers of the Antarctic.
4. These results pave the way for a future ESA satellite, CryoSat, with the capability of measuring ice thickness to an even smaller scale, and extend coverage to within 200km of the North Pole.
5. The Centre for Polar Observation and Modelling at UCL is one of NERC's centres of excellence in earth observation. NERC specialises in earth system science, covering the full range of atmospheric, earth, terrestrial and aquatic sciences, working with scientists and other partners around the world. It is addressing some of the key questions facing mankind such as global warming, renewable energy and sustainable economic development. More information at www.nerc.ac.uk or contact Marion O'Sullivan, NERC Press Officer, on 01793 411727.
6. For information about the Hadley Centre or to arrange an interview with Doug Smith, contact the Met Office press office on 01392 886655.
7. For further information, you can visit www.cpom.org, and visit the Media section (User name media, Password seattle)