Unstable Siberian Arctic Shelf Releases Twice the Amount of Methane
The frozen permafrost under the East Siberian Arctic Shelf once considered an impermeable barrier trapping in methane, has lately showed signs of instability and started leaking tons of methane into the atmosphere each year. A latest finding claims that the amount of methane released by the Arctic seafloor is twice the previous estimates.
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According to the study results reported in the journal Nature Geoscience, the East Siberian Arctic shelf, a methane rich area that includes over two million square kilometer of seafloor in the Arctic Ocean, is releasing nearly 17 tetragrams (1 tetragram=1 million tons) of methane in the atmosphere each year.
Methane is a potent greenhouse gas. The Arctic region has several methane sources and at the same time it is one of the fastest warming regions on the planet. It was estimated earlier by several scientists that even a fraction of this greenhouse gas present in the ice shelf could cause an abrupt climate warming.
"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, one of the paper's lead authors and a scientist at the University of Alaska Fairbanks, said in a statement. "Increased methane releases in this area are a possible new climate-change-driven factor that will strengthen over time."
Methane that is 30 times more potent that carbon dioxide is released on land when the once frozen organic material decomposes. In sea beds, the greenhouse gas is stored as a pre-formed gas or in the form of methane hydrates. The methane is trapped as long as the subsea permafrost is frozen but as the permafrost melts it develops holes through which the trapped methane vents out. This release is larger and abrupt when compared to the release that occurs due to decomposition.
This latest finding comes from the ongoing international research project led by Shakhova and Igor Semiletov, researchers at the UAF Inyernational Arctic Research Center. The twice yearly expeditions reveal that the subsea permafrost in the region has melted to a greater extent than was previously believed. This melting has created conditions that trigger the release of trapped methane in greater amounts than what the previous models had estimated. Frequent storms in the region further accelerate the release of methane into the atmosphere.
"Results of this study represent a big step forward toward improving our understanding of methane emissions from the East Siberian Arctic Shelf," said Shakhova. She noted that while the ESAS is unusual in its expansive and shallow nature, there is a need for further exploration of the subsea Arctic. "I believe that all other arctic shelf areas are significantly underestimated and should be paid very careful attention to."
To determine the conditions of water and permafrost, the researchers used a combination of several techniques such as sonar and visual images of methane bubble in the shallow water, sample of air and water, seafloor drilling and temperature readings. Using this they also determined the amount of methane that is being released.
Shakhova concluded, "We believe that the release of methane from the Arctic, and in particular this part of the Arctic, could impact the entire globe. We are trying to understand the actual contribution of the ESAS to the global methane budget and how that will change over time."