Rate of ice melt shocks warming experts

'The Arctic is screaming,' says one; another calls 2007 a 'watershed year'

WASHINGTON - An already relentless melting of the Arctic greatly accelerated this summer, a warning sign that some scientists worry could mean global warming has passed an ominous tipping point. One even speculated that summer sea ice would be gone in five years.
Greenland's ice sheet melted nearly 19 billion tons more than the previous high mark, and the volume of Arctic sea ice at summer's end was half what it was just four years earlier, according to new NASA satellite data obtained by The Associated Press.

"The Arctic is screaming," said Mark Serreze, senior scientist at the U.S. government's National Snow and Ice Data Center in Boulder, Colo.
Sea ice, which floats on water, is a key climate signal as well as prime habitat for walruses and polar bears in the Arctic. Ice sheets, for their part, lock water on land but raise sea levels if that ice starts to melt.

Changes in Arctic weather, especially warmer temperatures, also has implications for the rest of the world.

In the United States, a weakened Arctic blast moving south to collide with moist air from the Gulf of Mexico can mean less rain and snow in some areas, including the drought-stricken Southeast, said Michael MacCracken, a former federal climate scientist who now heads the nonprofit Climate Institute. Some regions, like Colorado, would likely get extra rain or snow.

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