Arctic Sea Ice Melts in Winter

Thursday, September 14 2006 @ 12:44 PM MDT
By bracewell

Arctic sea ice shrinks, a sign of greenhouse effect
Arctic perennial sea ice (year-round ice) declined by 14 percent between 2004 and 2005, what is new, and remarkable to scientists, is that the decline has been observed in winter as well as summer. Josefino Comiso of NASA's Goddard Space Flight Center outside Washington DC. "The winter warming signal is finally coming out."

Summer sea ice has also declined dramatically in recent years, but 2006 is unlikely to eclipse 2005's record for summer ice-melt.

One image showed a strange big hole in the summer ice north of Alaska. The hole, called a polynya, is probably about the size of the state of Maryland. Such a feature has never been seen in this area before, Serreze said.

The polar bear population in Canada's Hudson Bay has dropped from 1,200 in 1989 to about 950 in 2004, a decline of 22 percent,

Arctic Ice Melting Rapidly, Study Says
�It has never occurred before in the past," said NASA senior research scientist Josefino Comiso. Scientists have long worried about melting Arcticsea ice in the summer, but they had not seen a big winter drop in sea ice, even though they expected it. The ice is melting even in subfreezing winter temperatures because the water is warmer and summer ice covers less area and is shorter-lived.

From 2004 to 2005, the amount of ice dropped 2.3 percent; and over the past year, it's declined by another 1.9 percent, according to Comiso.
A second NASA study by other researchers found the winter sea ice melt in one region of the eastern Arctic has shrunk about 40 percent in just the past two years.

The latest findings are "coming more in line with what we expected to find," said Mark Serreze, a senior research scientist at the National Snow and Ice Data Center in Boulder, Colo. "We're starting to see a much more coherent and firm picture occurring. I hate to say we told you so, but we told you so," he added. Serreze said only five years ago he was "a fence-sitter" on the issue of whether man-made global warming was happening and a threat, but he said recent evidence in the Arctic has him convinced.

Equally disturbing is a large mass of melted sea ice - in the interior of a giant patch of ice north of Alaska. While those show up from time to time, this one is large and in an unexpected place. "I for one, after having studied this for 20 years, have never seen anything like this before," Serreze said.

Arctic Ice Meltdown Continues With Significantly Reduced Winter Ice Cover
ORIGINAL NASA ARTICLE

Using satellite data, scientists have observed unusually warm wintertime temperatures in the region and a resulting decline in the length of the Arctic ice season. "This amount of Arctic sea ice reduction the past two consecutive winters has not taken place before during the 27 years satellite data has been available,"

Adding to the plight of winter sea ice, previous research has shown a trend in which the melt period lasts about two weeks longer per year annually due to summer sea ice decline. This means that the onset of freeze-up is happening later in the fall season. As a result, the ice cover in winter never gets as extensive as it would have been if the freeze-up had begun earlier. More than that, the ice reflects the sun's radiation much more efficiently than the ocean's surface. As a result, as the ice cover declines, the ocean's surface warms, causing in turn, further decline of the ice.

According to Comiso, if the winter ice retreat continues, the effect could be very profound, especially for marine animals. "Some of the richest fisheries are found in the region, in part because of sea ice. Sea ice provides melt-water in spring that floats because of low density. This melt-water layer is considered by biologists as the ideal layer for phytoplankton growth because it does not sink, and there is plenty of sunlight reaching it to enable photosynthesis. Plankton are at the bottom of the food web. If their concentration goes down, animals at all tropics level would be deprived of a basic source of food."

Warming Climate May Put Chill on Arctic Polar Bear Population

The new research suggests that progressively earlier breakup of the Arctic sea ice, stimulated by climate warming, shortens the spring hunting season for female polar bears in Western Hudson Bay and is likely responsible for the continuing fall in the average weight of these bears. As females become lighter, their ability to reproduce and the survival of their young decline. Also, as the bears become thinner, they are more likely to push into human settlements for food, giving the impression that the population is increasing.

"In 1980 the average weight of adult females in western Hudson Bay was 650 pounds. Their average weight in 2004 was just 507 pounds � a 143-pound reduction," said Stirling. A 1992 study in the Canadian Journal of Zoology indicated that no females weighing less than 416 pounds gave birth the following spring.