University of Illinois Champaign-Urbana Arctic climate expert William Chapman told AFP that Arctic sea ice had plunged to new lows some 30 days before the normal point of the annual minimum.

He also said that with a lower ice cover and fewer clouds this year, the waters of the Arctic are being exposed to more intense sunlight, further warming them.

"As of yesterday and today ... we have set a historical low for sea ice in the northern hemisphere," he said.

Chapman, a researcher on Arctic meteorology of the university's Department of Atmospheric Sciences, wrote Thursday in the online publication "The Cryosphere Today" that the new record comes a full month before the historic summer minimum typically occurs during the first or second week of September.

"There is still a month or more of melt likely this year. It is therefore almost certain that the previous 2005 record will be annihilated by the final 2007 annual minima closer to the end of this summer."

He told AFP that current summer ice cover in the northern hemisphere is averaging 25-30 percent below what it was 50 years ago.

"The trend has been going down since the late 1970s at least, and maybe 50 years," he said.

Chapman said there are a few factors at work to cause the sharp dip this year.

One is the late freeze last autumn and a second, the early thaw in spring 2007. "The ice was not around for as long as it usually is," he said.

"The earlier spring melt opens up more dark water to sun," he added, helping the sea ice to melt faster.

Yet another factor is the uncommon low level of clouds this summer in the far north.

"This summer is also relatively clear, not 90 percent cloudy as usual," he said, allowing more sun to warm the waters and melt the ice.

"The concern is that the Arctic ocean is absorbing a lot of heat."

While immediate weather circumstances explain the plunge in ice cover this year, Chapman linked it all to the greater trend of global climate change.

"It is certainly likely that the overall trend is related to global warming."

One interesting aspect this year, he pointed out in his online article, is that the drop in sea ice is more geographically sweeping than in previous low years.

In earlier low years, big drops in the level of sea ice were confined to specific areas, such as the North Atlantic, the Bering Sea, the Beaufort Sea, or other locales.

This comes in part from prevailing winds blowing ice from one area or sea to another.

"The character of 2007's sea ice melt is unique in that it is dramatic and covers the entire Arctic sector," he wrote.

"Atlantic, Pacific and even the central Arctic sectors are showing large negative sea ice area anomalies."

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