Arctic sea ice forecast: another record low in 2008

WASHINGTON (Reuters) - Arctic sea ice, sometimes billed as Earth's air conditioner for its moderating effects on world climate, will probably shrink to a record low level this year, scientists predicted on Wednesday.

In releasing the forecast, climate researcher Sheldon Drobot of the University of Colorado at Boulder called the changes in Arctic sea ice "one of the more compelling and obvious signs of climate change."

If that prediction holds true, it would be the third time in the past five years that Arctic sea ice retreated to record lows, the scientists said in a statement. That retreat is caused by warming temperatures and the spread of younger, thinner, less hardy ice in the region.

Based on satellite data and temperature records, the researchers forecast a 59 percent chance the annual minimum sea ice record would be broken again in 2008.

In the past decade, Arctic sea ice declined by roughly 10 percent, with a record drop in 2007 that left a total minimum ice cover of 1.59 million square miles. That represented a decline of 460,000 square miles from the previous record low in 2005 -- an area the size of Texas and California combined. Scientists measure ice cover at its low ebb at the end of summer.

"The current Arctic ice cover is thinner and younger than at any previous time in our recorded history, and this sets the stage for rapid melt and a new record low," Drobot said.

Overall, 63 percent of the Arctic ice cover is younger than average, and only 2 percent is older than average, he said.

If Arctic sea ice keeps melting, it could hurt local wildlife, including polar bears, walruses and seals, the scientists said.

For humans, however, larger areas and longer periods of open Arctic water could make for cheaper merchant shipping between Europe and North America.

Arctic sea ice helps cool the planet with its usually reliable stores of white, sun-reflecting sea ice.

Sea ice melts and refreezes seasonally, but recent years have shown a smaller area of maximum sea ice in the winter, which suggests it is more difficult to restock the supply of polar ice after a record summer melt like last year's.

(Editing by Peter Cooney)