Aalok Mehta aboard the C.C.G.S. Amundsen
National Geographic News
Arctic warming has become so dramatic that the North Pole may melt this summer, report scientists studying the effects of climate change in the field.
"We're actually projecting this year that the North Pole may be free of ice for the first time [in history]," David Barber, of the University of Manitoba, told National Geographic News aboard the C.C.G.S. Amundsen, a Canadian research icebreaker.Firsthand observations and satellite images show that the immediate area around the geographic North Pole is now mostly annual, or first-year, ice—thin new ice that forms each year during the winter freeze.
Such ice is much more prone to melting during the summer months than perennial, or multiyear, ice, which is thick and dense ice that has lasted through multiple cycles of thawing and refreezing.
"I would say the ice in the vicinity of the North Pole is primed for melting, and an ice-free North Pole is a good possibility," Sheldon Drobot, a climatologist at the Colorado Center for Astrodynamics Research at the University of Colorado, said by email.
The melt would be mostly symbolic—thicker ice, pushed against the Canadian continental shelf by weather and Earth's rotation, would still survive the summer.
Recent models suggest that the Arctic won't see its first completely ice-free summer until somewhere between 2013 and 2030.
But this summer's forecast—and unusual early melting events all around the Arctic—serve as a dire warning of how quickly the polar regions are being affected by climate change.
Massive Melt
Scientists are particularly interested in the North and South Poles because they are expected to show the most dramatic effects of global warming.
Models predict that the regions will see temperature increases roughly three times as quickly as the rest of the globe because of an effect known as ice albedo feedback, which occurs when highly reflective ice gives way to dark water.
The water absorbs much more of the sun's energy, increasing temperatures and causing further ice melting.
"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.
"Endangered Species"
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."
from: http://news.nationalgeographic.com/news/2008/06/080620-north-pole.html
