Polar Ice Cap Shrinks Further and Thins

By GAUTAM NAIK

A decade-long decline in the ice covering the Arctic Sea is continuing, according to new U.S. data, and other measurements give fresh indications that the area's ice cap is thinning as well.
Associated Press
A polar bear swims near ice floes in Baffin Bay in the Arctic last summer. The Arctic melt is affecting tourism, shipping and trade routes.
Acting like a giant mirror, the Arctic sea ice helps cool the planet by reflecting solar radiation back into space. When there is less sea ice, the dark, open water absorbs more of the sun's warmth and raises the temperature of both air and water -- thereby affecting the climate.
How the sea-ice cover changes -- in both summer and winter -- has become a hot topic for policy makers. The Arctic melt is already affecting tourism, shipping and trade routes. It has persuaded several countries to push for territorial claims in newly accessible regions of the Arctic.
The latest figures were released the same day that Secretary of State Hillary Clinton opened a U.S.-hosted summit in Baltimore, which brings together two diplomatic bodies that govern the Arctic and Antarctic. The Obama administration is arguing for more restrictions on polar tourism to protect the fragile environment.
Scientists calculate that thicker ice that is two or more years old now makes up less than 10% of the Arctic's wintertime ice cover, about one-third the average levels seen annually from 1981 to 2000, according to a study reported Monday by a team of scientists at the University of Colorado at Boulder. That is equivalent to a decline of 278,000 square miles of ice, a surface area larger than Texas.
Equally troubling to some scientists is that the overall Arctic ice cap is thinning. That has been hard to measure in the past because the Arctic is vast, and because sea ice can move.
Scientists from the National Aeronautics and Space Administration's Jet Propulsion Laboratory in Pasadena, Calif., have now used satellite data to create the first map of sea ice over the entire Arctic basin. Their chief finding, based on data from 2005 and 2006, is that older arctic ice is on average nearly nine feet thick. Submarine measurements from the 1980s found that the ice then had been more than 4½ feet thicker, according to Ronald Kwok of NASA's Jet Propulsion lab.
"The sea-ice changes we're seeing go hand-in-hand with temperature changes," says Walt Meier of the National Snow and Ice Data Center at the University of Colorado. "There really isn't another overriding mechanism we see that can cause these long-term changes."
Concern over the polar environment comes amid a tussle in the U.S. over climate change. President Barack Obama and Democratic leaders in Congress have said they want a cap on greenhouse-gas emissions -- a departure from the policy of the Bush administration. Last week,, two House Democrats, Rep. Henry Waxman of California and Rep. Edward Markey of Massachusetts, introduced a bill to cut greenhouse-gas emissions 20% below 2005 levels by 2020, a bigger cut than Mr. Obama has called for in the same period.
Either way, the proposals represent only opening salvos in the political fight. Politicians from states that depend for most of their electricity on burning coal, which emits large amounts of greenhouse gases, already are warning that a severe emissions cap could significantly raise energy prices.
Given that debate, it is unclear whether the U.S. will have a climate proposal with broad political support by the time diplomats from around the world meet in December in Copenhagen to discuss a new international climate-change treaty.—Jeffrey Ball contributed to this article.
Write to Gautam Naik at gautam.naik@wsj.com