ANCHORAGE - Federal wildlife monitors spotted nine polar bears in one day swimming in open ocean off Alaska's northwest coast, and environmental groups say the event is a strong signal that diminished sea ice brought on by warming has put U.S. bears at risk of drowning or dying from effects of fatigue.
"The impact of global warming is brutal and tragic for polar bears," said Kassie Siegel of the Center for Biological Diversity. "The only way to limit the number of bears that will drown and starve is to reduce greenhouse gas pollution immediately."
The number spotted Saturday on long-distance swims in the Chukchi Sea was higher than has been seen in similar surveys.
Polar bears spend most of their lives on sea ice, which they use as a platform to hunt their primary prey, ringed seals. Polar bears are powerful swimmers, but are at increased risk of drowning in high wind and rough seas, Siegel said.
Conditions last weekend, Siegel said, were similar to those that preceded drownings in September 2004. Four polar bear carcasses were spotted in the Beaufort Sea after a storm, and federal scientists extrapolated that others probably died.
Department of Interior Secretary Dirk Kempthorne in May declared polar bears a threatened species because of an alarming loss of summer sea ice in recent decades and climate models that indicate the trend will continue.
Summer sea ice last year shrunk to a record low, about 1.65 million square miles in September, nearly 40 percent less than the long-term average between 1979 and 2000 and most climate modelers predict a continued downward spiral, possibly with an Arctic Ocean that's ice free during summer months by 2030 or sooner.
Conservation groups fear that one consequence of less ice will be more energy-sapping, long-distance swims by polar bears trying to reach feeding, mating or denning areas.
The nine bears were spotted on a flight by a marine contractor, Science Applications International Corp., hired for the Minerals Management Service in advance of future offshore oil development.
The MMS in February leased 2.76 million acres within an offshore area slightly smaller than Pennsylvania.
Observers Saturday were looking for whales, especially bowheads, said project director Janet Clark, but they also record walrus and polar bears.
The bears ranged from 15 to 65 miles off shore. Many were swimming north, Clark said.
Shallow water over the continental shelf is the most biologically productive for seals, but pack ice in recent years has receded far beyond the shelf. Polar bears have had the choice of staying with the pack ice hundreds of miles off shore or remaining on land where they cannot hunt seals, Siegel said.
Satellite data Saturday showed the main body of pack ice about 400 miles off shore with one ribbon about 100 miles off Alaska's coast, said Mark Serreze of the National Snow and Ice Data Center.
Clark said the flight was a snapshot of marine mammals and their origin and destination could not be known without radio collar monitoring.
"To go out there and say they were going from this point to this point would be complete speculation," Clark said.
Steven Amstrup, senior polar bear scientist for the U.S. Geological Survey in Anchorage, said the bears could have been on a patch of remaining sea ice that broke up northwest of Alaska's coast.
"The bears that had been on that last bit of ice that remained over shallow shelf waters, are now swimming either toward land or toward the rest of the sea ice, which is a considerable distance north," he said in an e-mail response to questions.
It probably is not a big deal for a polar bear in good condition to swim 10 or 15 miles, Amstrup said, but swims of 50 to 100 miles are probably a different matter energetically.
"We have some observations of bears swimming into shore when the sea ice was not visible on the horizon," he said. "In some of these cases, the bears arrive so spent energetically, that they literally don't move for a couple days after hitting shore."