Large amounts of methane leaked into atmosphere from Arctic shelf

13:41, March 06, 2010      

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The permafrost under the East Siberian Arctic Shelf is perforated and is starting to leak large amounts of methane into the atmosphere, sparking worries about climate warming, according to a new study.

The methane releases from Arctic shelf may be much larger and faster than anticipated, researchers at the University of Alaska said in the study published in the March 5 edition of the journal Science.

Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming, experts warn.

A section of the Arctic Ocean seafloor that holds vast stores of frozen methane is showing signs of instability and widespread venting of the powerful greenhouse gas, according to the findings.

"The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world's oceans," said lead researcher Natalia Shakhova. "Subsea permafrost is losing its ability to be an impermeable cap. "

The research results showed that the East Siberian Arctic Shelf is already a significant methane source, releasing seven teragrams of methane yearly, which is as much as is emitted from the rest of the ocean. A teragram is equal to about 1.1 million tons.

"Our concern is that the subsea permafrost has been showing signs of destabilization already," Shakhova said. "If it further destabilizes, the methane emissions may not be teragrams, it would be significantly larger."

Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. It is released from previously frozen soils in two ways. When the organic material (which contains carbon) stored in permafrost thaws, it begins to decompose and, under anaerobic conditions, gradually releases methane.

Methane can also be stored in the seabed as methane gas or methane hydrates and then released as subsea permafrost thaws. These releases can be larger and more abrupt than those that result from decomposition.

The East Siberian Arctic Shelf is a methane-rich area that encompasses more than two million square kilometers of seafloor in the Arctic Ocean. It is more than three times as large as the nearby Siberian wetlands, which have been considered the primary Northern Hemisphere source of atmospheric methane.

"The release to the atmosphere of only one percent of the methane assumed to be stored in shallow hydrate deposits might alter the current atmospheric burden of methane up to three to four times," Shakhova said. "The climatic consequences of this are hard to predict."

Source: Xinhua
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