By Deborah Zabarenko, Environment Correspondent
This year's Arctic ice melt could surpass the extraordinary 2007 record low in the coming weeks. Last year's minimum ice level was reached on September 16, according to the National Snow and Ice Data Center.
Even if no records are broken this year, the downward trend in summer sea ice in the Arctic continues, the Colorado-based center said. Last year's record was blamed squarely on human-spurred climate change.
"No matter where we stand at the end of the melt season it's just reinforcing this notion that Arctic ice is in its death spiral," said Mark Serreze, a scientist at the center. The Arctic could be free of summer ice by 2030, Serreze said by telephone.
This year's data "primarily reflects melt in the Chukchi Sea off the Alaskan coast and the East Siberian Seas off the coast of eastern Russia," the center said.
The Chukchi Sea is home to one of the world's largest polar bear populations and also includes a vast area where the United States sold oil and gas rights worth $2.66 billion last year.
On Tuesday, Arctic sea ice stretched over 2.03 million square miles, which is less than the 2005 mark of 2.05 million square miles, set on September 21 of that year, the center's analysis found.
The record drop in 2007 left a minimum ice cover of 1.59 million square miles. The fabled Northwest Passage was open for the first time in memory.
Government scientists reported seeing at least nine polar bears swimming in open water over a six-hour period on August 16, including one more than 50 miles offshore, World Wildlife Fund officials said.
LONGER SWIMS FOR POLAR BEARS
That represents a huge increase over previous sightings, said Margaret Williams of the fund's Alaska office. A total of 12 polar bears were spotted in open water between 1987 and 2003, Williams said in a telephone interview.
In 2004, she said, four drowned bears were observed.
"Unfortunately it's what we might expect to see if bears are forced to swim longer distances," Williams said. "The Arctic is gigantic. When you have nine bears sighted in one transect (route) ... one can assume that there are likely a lot more bears swimming in open water."
She noted that bears are capable swimmers and rely on sea ice as platforms for hunting seals, their main prey. If relegated to land, bears have little to hunt and sometimes feed on carrion or garbage and can be a threat to humans.
As more Arctic ice melts, bears are forced to swim longer distances to find adequate platforms for hunting. Rescuing bears in distress in open water is problematic, Williams said: tranquilizing the bears sends them into the water to drown.
The U.S. government in May listed polar bears as a threatened species because their icy habitat was disappearing, but offered no plans to address climate change or drilling in the Arctic for fossil fuels that spur the climate-warming greenhouse effect.
Summer ice melt in the Arctic is seen as a strong indicator of climate change, and feeds on itself in what scientists call a positive feedback loop where warming exposes dark sea water, which absorbs more solar radiation than the white ice.
Arctic sea ice is sometimes dubbed Earth's air conditioner for its ability to moderate world climate. In the last decade, this ice has declined by roughly 10 percent.
(Editing by Sandra Maler)