Scientists took sonar measurements to record clouds of methane bubbles rising from the seafloor. Photo: Igor Semiletov, University of Alaska
More evidence is emerging that methane previously trapped in the permafrost below the Arctic sea is starting to be released into the oceans and potentially into the atmosphere. Research published in Science shows that up to 7 million tons of methane is released annually from the East Siberian Arctic Shelf--a small percentage of total greenhouse gas emissions, but potentially enough to account for recent increases in atmospheric methane levels.
The permafrost of the East Siberian Arctic Shelf (an area of about 2 million kilometers squared) is more porous than previously thought. The ocean on top of it and the heat from the mantle below it warm it and make it perforated like Swiss cheese. This allows methane gas stored under it under pressure to burst into the atmosphere. The amount leaking from this locale is comparable to all the methane from the rest of the world's oceans put together. Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. Image: Zina Deretsky, National Science Foundation
Study lead author Natalia Shakhova said it was too early to say if we're about to pass a tipping point where massive amounts of stored methane are released into the atmosphere, triggering rapid warming, but that is a concern.
Our concern is that the subsea permafrost has been showing signs of destabilization already. If it further destabilizes, the methane emissions may not be teragrams [one million metric tons], it would be significantly larger.
Remember that methane is at least 25 times more potent than CO2 in terms of its warming potential--if just 10% of the methane stored in Arctic permafrost were released into the atmosphere it could lead to a further 0.7°C warming all on its own, equivalent to all the warming the world has seen since the industrial revolution.
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