Vast amounts of methane are bubbling up from the East Siberian sea, raising fears of a massive hike in global warming.
Permafrost in the seabed has been previously assumed to act as an effective cap for the enormous amount of methane in the area.
But researchers at the Russian Academy of Sciences, the University of Alaska and Stockholm University have found that eight million tonnes of methane are currently leaking into the atmosphere every year.
"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. "Subsea permafrost is losing its ability to be an impermeable cap."
It's not known how long the methane release has been going on. But models suggest that if just one percent of the methane contained in the region were released, it would cause rapid warming.
Earlier periods of rapid climate change have been associated with sudden releases of methane from the seabed.
During the ISSS expedition measurements of methane were made in the seabed, at different depths in the water and in the overlying air at over one hundred locations.
Combined with measurements from previous expeditions, it was found that methane concentrations in seawater are elevated in 80 percent of sea bottom samples and in more than half of the surface water samples and air samples.
Some areas had concentrations up to 100 times above the natural background levels, and the ISSS expedition discovered methane chimneys on the ocean floor and fields of methane bubbles that rose to the surface of the sea so fast that the methane did not have time to dissolve in the seawater.
"Our concern is that the subsea permafrost has been showing signs of destabilization already," she said. "If it further destabilizes, the methane emissions may not be teragrams, it would be significantly larger."
The full study appears in Science.