Methane leak from Arctic Shelf may be much larger and faster than anticipated

Washington, March 5 (ANI): An international team of scientists has found that the permafrost under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is starting to leak large amounts of methane into the atmosphere.

The research team, led by University of Alaska Fairbanks scientists Natalia Shakhova and Igor Semiletov, found that the Arctic Shelf, which holds vast stores of frozen methane, is showing signs of instability and widespread venting of the powerful greenhouse gas.

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 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 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 2 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.

Shakhova's research results show that the East Siberian Arctic Shelf is already a significant methane source, releasing 7 teragrams of methane yearly, which is as much as is emitted from the rest of the ocean.

"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," she added.

Methane levels throughout the Arctic are usually 8 to 10 percent higher than the global baseline.

When the research team flew over the shelf, they found methane at levels another 5 to 10 percent higher than the already elevated Arctic levels.

The East Siberian Arctic Shelf, in addition to holding large stores of frozen methane, is more of a concern because it is so shallow.

In the shallows of the East Siberian Arctic Shelf, methane simply doesn't have enough time to oxidize, which means more of it escapes into the atmosphere.

That, combined with the sheer amount of methane in the region, could add a previously uncalculated variable to climate models. (ANI)