Orjan Gustafsson (left) and Martin Kruså take sediment samples in the sea north of Siberia during the arctic expedition, 2008. Photo: Jorien Vonk
Orjan Gustafsson (left) and Martin Kruså take sediment samples in the sea north of Siberia during the arctic expedition, 2008. Photo: Jorien Vonk

The sediments of the shallow Siberian Seas are believed to hold an amount of methane equaling approximately 200 times the amount of methane present in the atmosphere. The current venting of methane from the Siberian Arctic Ocean to the atmosphere is larger than the total flux from the rest of the World Ocean. While the high methane concentrations in the seawater demonstrate that the subsea permafrost is thawing and releasing methane, the flux is at present not acutely affecting the global atmospheric methane balance.  

The research team combined thousands of methane measurements in the seawater over a 12 year period with drilling 50 m into the seabed of the Laptev Sea and geophysical sonar techniques to  quantify the significant amounts of methane that are bubbling up from the seabed.

 “We have proven that the current thermal state of subsea permafrost is incomparably closer to or even at the thaw point than terrestrial (land-based) permafrost, and that modern warming does contribute to warming the subsea permafrost,” says Natalia Shakhova, lead study author and a biogeochemist at the University of Alaska, Fairbanks, adding that an increase in storminess in the Arctic would further speed up the release of methane to the atmosphere. 

The new estimate of some 17 million tons of methane escaping annually from the Shelf sediments to the Arctic atmosphere is now doubling a first estimate from the team published in the journal Science in 2010.  “While we had seen bubbles earlier, in the 2010 study we were only able to quantify the atmospheric release from methane dissolved in surface seawater”, explains Örjan Gustafsson, a co-author of both studies, and a professor at Stockholm University, and continues, “the use of sonar equipment in the new study allowed us now to quantify also the bubble-transported methane fluxes”. 

The methane in the subsea sediments can exist in several forms: (i) methane associated with permafrost that was earlier on land but drowned by rising sea level at termination of the last ice  age some 7000 years ago, (ii) as frozen methane hydrates within and below the subsea permafrost, and (iii)  as huge bubbles/pockets of natural gas rising from deep petroleum sources and presumably held back by the now thawing permafrost lid. 

In order to predict the future development of these methane fluxes and the potential risk of abruptly increasing methane fluxes there is a large need to better understand both the temperature of the subsea permafrost and the relative contributions to the leaking methane from the different subsea methane pools. 

The next opportunity to probe this question is a 90-day Swedish-Russian-US expedition to the poorly investigated and inaccessible outer Siberian Arctic Shelf and Slope Seas onboard the Swedish icebreaker Oden, planned for the summer of 2014 as part of the Swedish-Russian-US Arctic Ocean Investigation of  Carbon-Climate-Cryosphere Interactions (the SWERUS-C3 Program, primarily funded by Knut and Alice Wallenberg Foundation).



Article in Nature Geoscience (Advanced Online version)
Ebullition and storm-induced methane release from the East Siberian Arctic Shelf  by Shakhova, N., I . Semiletov, I. Leifer, V. Sergienko, A. Salyuk, D. Kosmach, D. Chernykh, C. Stubbs, D. Nicolsky, V. Tumskoy, Ö. Gustafsson


For further information contact:

Professor Örjan Gustafsson, Department of Applied Environmental Science and the Bolin Centre for Climate Research, Stockholm University

Email: orjan.gustafsson@itm.su.se

Phone: +46-70-3247317

For expedition images and video clips from the East Siberian Arctic Ocean, contact:

Stockholm University Press Office

Email: press@su.se
Phone: +46 (0)8-164090