The arctic seafloor is releasing methane, a greenhouse gas linked to global warming, at more than twice the rate previously estimated, scientists say.
U.S. researchers reporting in the journal Nature Geoscience say the seafloor off the coast of Northern Siberia, known as the East Siberian Arctic Shelf, is venting at least 17 million tons of methane into the atmosphere each year.
"It is now on par with the methane being released from the arctic tundra, which is considered to be one of the major sources of methane in the Northern Hemisphere," Natalia Shakhova of the University of Alaska Fairbanks said.
As a greenhouse gas, methane is 30 times more potent than carbon dioxide. On land, it is released when previously frozen organic material decomposes, while in the seabed it can be stored as a preformed gas or as hydrates.
Frozen subsea permafrost can keep the methane trapped, holding it beneath the seafloor, but if the permafrost thaws the methane can escape in releases larger and more abrupt than those on land, the researchers said.
Methane is an important factor in global climate change, because it effectively traps heat.
"Increased methane releases in this area are a possible new climate-change-driven factor that will strengthen over time," Shakhova said. "We believe that the release of methane from the arctic, and in particular this part of the arctic, could impact the entire globe."
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Original headline: Arctic releases of methane could drive up global warming
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