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Retreating Arctic Ice Caps Could Affect Global Climate - 2003-10-25


U.S. satellite observations show a continuing retreat of the North Pole ice cap, as the Arctic warms. Scientists say the shrinking ice cover feeds global warming, but is also enhanced by it in a vicious cycle. Small changes can have a big impact on our lives.

One year ago, the U.S. space agency NASA reported that the permanent Arctic ice layer covered less area than at any time since satellite measurements began. The agency found that Arctic temperatures were increasing about one degree Celsius a decade, with a corresponding ice cap loss of nine percent per decade. It warned that the ice could disappear in this century, if the trend continued.

Now, the NASA researcher who published those findings, Josefino Comiso, said the trend is continuing. "Come this year, the perennial ice cover was almost as low as that of the previous year. In fact, the Arctic is in the process of being transformed," she said.

The rate of decline is expected to accelerate. As Arctic temperatures increase, the ice cover retreats more, exposing more ocean to the sun, warming the water, which melts more ice. At the same time, the warmer water heats the atmosphere, contributing to global warming. University of Colorado scientist Mark Serreze explains.

"Sea ice is a very effective insulator in that it tends to insulate the warm ocean from the cold atmosphere. Well, if we begin to retreat the sea ice, we expose that ocean to the air, the atmosphere warms," Mr. Serreze said.

As the cycle continues, the researchers say, summers could lengthen, allowing earlier spring thaws and later fall freezes, causing further ice thinning.

University of Washington oceanographer Michael Steele said the retreating ice cover is already having an impact on life in the region, and could affect commerce. Ice-clogged shipping lanes will open among Asia, North America, and Europe. But there are also negative consequences.

"Hunting of marine animals tends to occur on sea ice, and when that sea ice retreats, it affects the communities up there. Another way communities are affected is when there is more open water, there is a longer distance over which wind can blow. So bigger waves are generated, creating a really severe coastal erosion problem in the north, to the extent that there are communities up in Alaska and other places that are having to move from low lying area to more sheltered areas," Mr. Steele said.

The highly populated middle latitudes in North America, Europe, the Middle East and Asia are not exempt, either. NASA climate expert David Rind designed a computer program that revealed the impact on these regions, only if Arctic ice disappeared without a corresponding temperature rise. The study suggested there would be, for illustration, setbacks to U.S. wheat production.

"In Kansas, for example, the winter temperatures were some four degrees Fahrenheit warmer, and snow cover was reduced by about 40 percent (in the projection). Winter wheat that is grown in Kansas requires these cold temperatures. If you don't get them, you have to switch to different, less productive forms of wheat. In addition, the snow cover provides moisture," Mr. Rind said.

No one can be certain whether Arctic warming and global warming in general are caused by natural climate variation or human activities. The general consensus - reflected by a United Nations panel of dozens of scientists from around the world - is that people are part of the problem, chiefly because gas emissions from cars and industry create a pollution shield that retains solar heat.

The University of Colorado's Mark Serreze said, whatever the cause, everyone should be concerned about Arctic warming.

"The fact is, climate is changing, and the Arctic is changing rapidly. We should be concerned in the sense that we need to simply recognize that change is here, change is occurring, and we may have to adapt to it," Mr. Serreze said.

For three days next [this] week [Oct. 27-30], researchers from around the world are meeting in Seattle, Washington, to discuss Arctic warming and the next steps they need to take to better understand the complex physical process that governs the region's environment.

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