Methane release 'could trigger abrupt warming'

Arctic seabed methane stores destabilizing, venting

University of Alaska, Fairbanks: 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... The research results... show that the permafrost under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is leaking large amounts of methane into the atmosphere. Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.

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 [Natalia] Shakhova, a researcher at UAF's International Arctic Research Center.

Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. It is released from previously frozen soils... 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... Current average methane concentrations in the Arctic average about 1.85 parts per million, the highest in 400,000 years... Concentrations above the East Siberian Arctic Shelf are even higher...

They found that more than 80 percent of the deep water and greater than half of surface water had methane levels more than eight times that of normal seawater. In some areas, the saturation levels reached at least 250 times that of background levels in the summer and 1,400 times higher in the winter... The methane was not only being dissolved in the water, it was bubbling out into the atmosphere... Methane levels throughout the Arctic are usually 8 to 10 percent higher than the global baseline. When they flew over the shelf, they found methane at levels another 5 to 10 percent higher than the already elevated arctic levels.

'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 3 to 4 times,' Shakhova said. 'The climatic consequences of this are hard to predict.'

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