Abrupt reversal detected in Arctic cooling trend

[Kadie]

Abrupt reversal detected in Arctic cooling trend

David Perlman, Chronicle Science Editor

Friday, September 4, 2009

The Arctic climate has been warmer over the past decade than during any 10-year period in 2,000 years, according to a study by an international research team that adds powerful new evidence that human-generated greenhouse gases have speeded the pace of the planet's recent warming.

he report from an international team of climate scientists concludes that climate change in the Arctic has accelerated since the Industrial Revolution, abruptly reversing a long-term worldwide cooling trend.

"The study provides a clear example of how increased greenhouse gases are now changing our climate," said Caspar Ammann of the National Center for Atmospheric Research in Boulder, Colo., a co-author of the report published Thursday in the journal Science.

To deduce the Arctic's decade-by-decade climate trend over the centuries, the leading scientists in the international study analyzed sediment cores in 14 Arctic lakes that revealed the varied growth rates of long-buried plants. They also studied Arctic tree rings to determine their growth rates and ages as well as ice cores from glaciers across the Arctic that showed patterns of relative warm and cold.

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2009/09/04/MNB219HIRT.DTL&tsp=1#ixzz0Q9TYB8Vo

[FarCenter]

1. New NASA Satellite Survey Reveals Dramatic Arctic Sea Ice Thinning

July 07, 2009 http://www.jpl.nasa.gov/news/news.cfm?release=2009-107

PASADENA, Calif. - Arctic sea ice thinned dramatically between the winters of 2004 and 2008, with thin seasonal ice replacing thick older ice as the dominant type for the first time on record. The new results, based on data from a NASA Earth-orbiting spacecraft, provide further evidence for the rapid, ongoing transformation of the Arctic's ice cover.

Scientists from NASA and the University of Washington in Seattle conducted the most comprehensive survey to date using observations from NASA's Ice, Cloud and land Elevation Satellite, known as ICESat, to make the first basin-wide estimate of the thickness and volume of the Arctic Ocean's ice cover. Ron Kwok of NASA's Jet Propulsion Laboratory in Pasadena, Calif., led the research team, which published its findings July 7 in the Journal of Geophysical Research-Oceans.

The Arctic ice cap grows each winter as the sun sets for several months and intense cold ensues. In the summer, wind and ocean currents cause some of the ice naturally to flow out of the Arctic, while much of it melts in place. But not all of the Arctic ice melts each summer; the thicker, older ice is more likely to survive. Seasonal sea ice usually reaches about 2 meters (6 feet) in thickness, while multi-year ice averages 3 meters (9 feet).

Using ICESat measurements, scientists found that overall Arctic sea ice thinned about 0.17 meters (7 inches) a year, for a total of 0.68 meters (2.2 feet) over four winters. The total area covered by the thicker, older "multi-year" ice that has survived one or more summers shrank by 42 percent.

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2. Climate trouble may be bubbling up in far north

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"On a calm day, you can see 20 or more `seeps' out across this lake," said Canadian researcher Rob Bowen, sidling his small rubber boat up beside one of them. A tossed match would have set it ablaze.

"It's essentially pure methane."

Pure methane, gas bubbling up from underwater vents, escaping into northern skies, adds to the global-warming gases accumulating in the atmosphere. And pure methane escaping in the massive amounts known to be locked in the Arctic permafrost and seabed would spell a climate catastrophe.

...snip...

In 2007, air monitors detected a rise in methane concentrations in the atmosphere, apparently from far northern sources. Russian researchers in Siberia expressed alarm, warning of a potential surge in the powerful greenhouse gas, additional warming of several degrees, and unpredictable consequences for Earth's climate.

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