That has been reflected in the satellite record, which shows a gradual decrease in the extent of Arctic ice coverage over the years.
But the North Pole's current plight stems from a much more startling reduction in sea ice that took place last summer. That extensive melt shattered all previous records and destroyed a significant portion of the Arctic's multiyear ice.
"We lost 65 percent of the ice cover in the Northern Hemisphere all in one year," Barber said. "So it was a whopping decrease. We didn't even think it was possible for the system to lose so much ice all at once."
Scientists say the record loss last year was due to a combination of warm ocean currents, fluke winds, and unusually sunny weather. (See: "Warming Oceans Contributed to Record Arctic Melt" [December 14, 2007].)
It's unlikely that such a mixture of conditions will occur again, University of Colorado's Drobot said.
But forecasts for this summer's ice suggest the damage has already been done.
An unusually cold winter had raised hopes for a recovery, but much of the ice that formed froze later than usual, ending up so thin that it has already started to break up.
Scientists are hesitant, however, to offer a definitive prediction specifically about the North Pole, since that is dependent on weather conditions that are highly erratic.
"Nobody knows for sure," Ron Lindsay, of the University of Washington, Seattle's Polar Science Center, said by email.
"While much of the first-year ice melts in the summer, not all of it does, so we can't be sure it will melt at the Pole," he said. "We also don't know what the winds will be like this summer, and they play an important role in determining just what parts of the Arctic Ocean are ice-free."
But given the rapid changes now evident in the Arctic, the ultimate fate of the North Pole—in fact, all permanent ice in the Arctic—may be all but assured. Almost all models have the Arctic completely ice free in the summer by 2100.
"We jokingly call [perennial ice] an endangered species," Barber said. "It's on its way out. And so we're studying it as quickly as we can, because there isn't going to be any of it left pretty soon."
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