Correction to This Article
The A-section article about the melting of the polar ice caps misspelled the name of Ted Scambos?, a researcher at the National Snow and Ice Data Center at the University of Colorado at Boulder.
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At the Poles, Melting Occurring at Alarming Rate

As the air warms over Canada, Alaska and Siberia, the melting permafrost releases millions of tons of trapped carbon and methane, further accelerating the encroaching disaster. Greenland's moving glaciers pick up speed, likely bringing in this century the first three feet of a possible 23-foot rise of the seas that would ultimately inundate New York City and South Florida and drive millions of people from low-lying areas of Asia.

The ice shelves collapsing in western Antarctica bring glacier melting there, pouring as much water into the sea as Greenland. Eventually, the giant frozen continent of eastern Antarctica, so far insulated from the rest of the warming planet, may begin to melt. The thermohaline ocean circulation pattern begins to slow.

"I just don't see a happy ending for this," said Ted Scanbos, who studies the polar ice at the National Snow and Ice Data Center at the University of Colorado.

Most scientists say the changes anticipated at the poles in the next 30 to 40 years are inevitable, and averting more severe effects will take a drastic reduction in emissions of greenhouse gases. Some have advanced controversial ideas to exploit the polar systems. At least three companies have plans to "fertilize" the Southern Ocean with iron try to soak more carbon dioxide out of the air.

"We are just leveraging a natural process," said Dan Whaley, founder of Climos, a San Francisco company. Other scientists gathered recently at the Woods Hole Oceanographic Institute were skeptical of the idea. "There will be scientific consequences we cannot predict," warned John Cullen, an oceanographer at Dalhousie University in Halifax.

The polar regions have been regularly described as the canaries in the coal mine of global warming: remote bellwethers that could give mankind a heads-up when important changes are coming.

Some even see positive opportunities in the warming. The legendary Northwest Passage, a sea route from the Atlantic to the Pacific above North America, is now mostly ice-free in the summer. That opens up tempting commercial possibilities for shippers and for drillers seeking vast oil and gas fields under the Arctic Ocean. Arctic nations including Canada, Norway, the United States and Russia are engaged in an increasingly urgent race to map out the ocean floor and stake claims on undersea resources.

But it turns out that the polar regions are far more than simple alarms. What happens at the poles will -- and is -- affecting the rest of the world.

Consider the permafrost. The vast Arctic region in the north encompasses land on three continents that has been deeply frozen since the last ice age. A thin layer thaws each summer. By mid-century, half of it will thaw to 10 feet, according to computer models of the National Center for Atmospheric Research in Boulder, and long-trapped greenhouse gases will be released.

Already, the melting in Siberia is releasing methane, a potent greenhouse gas, that had been buried for 40,000 years, feeding a cycle of more warming and more melting.

"That's a serious runaway," Scanbos said. "A catastrophe lays buried under the permafrost."

Or consider the ocean currents. The weather in the Northern Hemisphere is controlled by the temperature of currents that circulate on a giant treadmill, in which water cooled at the icy poles sinks to the bottom, and moves slowly toward the equator, where it heats and rises to flow northward again, mixing the seas. That is why Europe's climate is relatively moderate.

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