Arctic Sea-ice cover nears record low, heralds ice-free summers

Arctic sea-ice coverage this year approached last year's record low, reinforcing a trend that could see the Arctic Ocean completely ice-free in summer by 2060, US scientists monitoring the region said. Five of the six lowest values in a series dating back to 1979 have occurred in the past five years, said NSIDC research scientist Walt Meier. „That's really striking, and it probably means we're seeing the lowest values since at least 1900,” Meier said in a telephone interview from Boulder, citing measurements taken from ships and aircraft that predate the satellite record. „It does seem we're heading for an ice-free Arctic this century.”

The loss of summer ice over the Arctic, attributed to warmer temperatures, will have adverse effects for the indigenous peoples and the local wildlife of the Arctic, hampering their ability to hunt, Meier said. There will also be repercussions for marine transport and the possibility of prospecting for energy resources, he said. Sea-ice extent, the area of ocean covered by at least 15% ice, was about 5.7 million square kilometers (2.2 million square miles) according to a five-day average ending September 14, when this year's coverage was at its lowest, the NSIDC said yesterday in an e-mailed statement. That compares with the record low of 5.32 million square kilometers from September 21, 2005. Graphics on the center's Web site show that current coverage is about 1.5 million square kilometers below the 1979 to 2000 average for the time of year. Another phenomenon observed this year was the opening up within the sea ice of a stretch of water, known as a polynya, the size of Indiana, the statement said.

„This is by far the largest and most persistent open-water stretch in the Arctic satellite record,” Meier said of the polynya. He said its causes aren't fully known, with scientists positing three theories: that it was the result of a patch of thin ice melting, that winds kept the ice apart, or that warm waters welled up to the surface in that area. Yesterday's report from the NSIDC follows a study last month by the National Aeronautics and Space Administration that showed the Arctic's perennial sea ice, or the frozen water that usually doesn't melt during the summer, last winter shrank by about 720,000 square kilometers, an area the size of Texas. While overall ice coverage, which also includes thin seasonal ice, was stable over the winter, the proportion accounted for by perennial ice, 3 or more meters (10 or more feet) thick, decreased. While conditions may fluctuate year to year, the overall melting effect is expected to accelerate as a „feedback loop” sets in, whereby larger patches of open water absorb more heat over summer and freeze less easily over winter, Meier said. Accounting for that, ice-free summers may occur by 2060, he said.

 An ice-free Arctic could have knock-on effects in global climate patterns as winds and currents may change, according to Meier. Shipping across the ocean will become easier as the ice dwindles, and this year the North-west passage opened up for two to three weeks he said. The biggest effect may be suffered by wildlife, including polar bears, which rely on the ice to hunt. A US Minerals Management Service study presented in December indicated that polar bears were drowning because they had to swim farther in search of food. Meier said that further losses may drive the species to extinction, or confine it to a smaller territory. The National Snow and Ice Data Center is part of the University of Colorado's Cooperative Institute for Research in Environmental Sciences. (Bloomberg)