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Melting Arctic sea ice, the clearest indicator of global warming, has suddenly taken a big leap forward in the most ominous climate change development.  Two NASA studies show a surge in the loss of ice cover in two years.

Rapid changes in Arctic sea ice

15 September 2006

NASA data shows that Arctic perennial sea ice, which normally survives the summer melt season and remains year-round, shrunk abruptly by 14 percent between 2004 and 2005.

The loss of perennial ice in the East Arctic Ocean neared 50 percent during that time as some of the ice moved to the West Arctic.

The overall decrease in winter Arctic perennial sea ice totals 280,000 square miles - an area the size of Texas.

Perennial ice 10 feet or more thick was replaced by new, seasonal ice only about 1 to 7 feet thick that is more vulnerable to summer melt.

The decrease in the perennial ice raises the possibility that Arctic sea ice will retreat to another record low extent this year. This follows a series of very low ice-cover years observed over the past four summers.

A team led by Son Nghiem of NASA's Jet Propulsion Laboratory in Pasadena, California determined that while the total area of all the Arctic sea ice was stable in winter, the distribution of seasonal and perennial sea ice changed significantly.

"Recent changes in Arctic sea ice are rapid and dramatic," said Nghiem.  If the seasonal ice in the East Arctic Ocean is removed by summer melt, a vast ice-free area would open up.

Data from the National Centers for Environmental Prediction, Boulder, Colorado, suggest that winds pushed perennial ice from the East to the West Arctic Ocean (primarily located above North America) moving ice out of the Fram Strait, an area located between Greenland and Spitsbergen, Norway.

This ice movement out of the Arctic is a different mechanism for ice shrinkage than the melting of Arctic sea ice, but it also reduces the amount of perennial Arctic sea ice.

If sea ice continues to decline, the surrounding ocean will get warmer, further accelerating summer ice melt and impeding fall freezing. This longer melt season will, in turn, further diminish Arctic ice cover.

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Loss of winter Arctic sea ice increases dramatically

13 September 2006

The Arctic has experienced record low sea ice in the last two years.  In a study by NASA's Goddard Space Flight Center in Greenbelt, Maryland, satellite observations show unusually warm wintertime temperatures and a resulting decline in the length of the Arctic seasonal ice.

The amount of winter sea ice has fallen by 6 percent over each of the last two winters. The average annual loss is 1.5 percent per decade since satellite monitoring began in 1979.

This increased winter loss is occurring as summer sea ice continues its retreat at an average of 10 percent per decade.

"This amount of sea ice reduction the past two winters has not taken place before during 27 years that satellite data has been available," said NASA scientist Joey Comiso.  In the past, winter sea ice reduction was significantly lower than summer reduction.

The reduction in Arctic perennial sea ice (shown in white) is illustrated by the images in December 2004 (above left) and the same month in 2005 (above right). Interannual observations of sea ice over the Arctic have enabled the detection of recent drastic reduction in the extent of perennial ice and its depletion from the eastern Arctic Ocean. These changes have significant implications for the Arctic environment, navigation, and resource exploration.
Image credit NASA/JPL

View larger images

Image below: The winter sea ice cover during its annual maximum extent from 1979 to 2006, with the edge of the yellow area showing how far the winter ice cover extended to the south since 1979.
Image credit left and below NASA.

Computer simulations of the climate warming effect of greenhouse gases had predicted that winter sea ice would decline faster than summer sea ice. Satellite data has shown otherwise until two years ago, when record low winter ice cover and warmer temperatures have prevailed.

Sea ice cover in the Northern Hemisphere spans nearly 6.2 million square miles in the winter.

Adding to the plight of winter sea ice, previous research has shown a trend in which the melt period lasts about 2 weeks longer per year annually due to summer sea ice decline.

Comiso used satellite data from 1978 to 2006 to carry out the study, to be published in Geophysical Research Letters this month.

According to Comiso, "seasonal ice regions in the Arctic are among the most biologically productive regions in the world,". "For example, 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." "A continued reduction of the Arctic winter ice cover would be a clear indicator of the warming effect of increasing greenhouse gases in the atmosphere.

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