"North Pole ice 'may disappear by September'"

Ice at the North Pole may disappear completely within the next few months for the first time in 20,000 years.

Arctic sea ice is now retreating so quickly that scientists say there is now a 50-50 chance that it will have gone completely by September.

The Polar regions have been the first to show the critical changes brought by global warming and it will be a hugely symbolic moment if the North Pole is left surrounded by water.

The sight of ships able sailing to the Pole for the first time would be seized on by environmental groups as an example of the consequences of a failure to take action on a global scale to combat global warming.

The Arctic is seen as an important indicator of the potentially catastrophic changes that scientists say will come as the planet warms.

Scientists who monitor the Arctic say the volume of Arctic ice peaked in March and has been in dramatic decline since.

"There is supposed to be ice at the North Pole - not water," said Mark Serreze of the US National Snow and Ice Data Centre (NSIDC) in Colorado.

The Centre has been predicting that the Arctic Ocean could be virtually ice-free by 2012 but that point may be reached within months rather than years.

The extent of the ice stood at 5.59m square miles in April - 0.24m square miles more than it was in 2007 - but still less than the 1979-2000 average for April.

Although there is more ice than this time last year, the average decline rate through the month of April was 2,300 square miles per day faster than last April.

"Taken together, an assessment of the available evidence points to another extreme September sea ice minimum. Could the North Pole be ice free this melt season? Given that this region is currently covered with first-year ice, that seems quite possible," the Centre says in its latest bulletin.

First-year ice - which has replaced much of the thicker ice formed over millennia - is thinner and more vulnerable to melting,

The rapid decline has been due to the warm conditions over the Arctic and peripheral seas in April which in some areas was 5ºC higher than expected. Scientists say the warmer conditions were probably due to shifts in atmospheric circulation that brought warm air into the region....

Prof Peter Wadhams of Cambridge University, Professor of Ocean Physics and Head of the Polar Ocean Physics Group, who was the first scientist to study what was happening beneath the Arctic in a Royal Navy submarine, agreed that there was an even chance that the ice would disappear this year.

"It is certainly the case that ice has been disappearing and last year it disappeared almost completely. Small areas of the Pack Ice have opened up before but now we have open water at the very edge of the ice below the North Pole," he said.

"As far as we can tell this has not happened for at least 20,000 years. The real shock is that it has happened so quickly with ice formed in the winter melting by the summer.

"These are the big changes that have been predicted happening before our eyes. This is perhaps the first sign of what we are in for."