16th May 2012.
A new set of airborne observations has revealed high methane concentrations in the atmosphere above the Arctic Ocean. The concentration of methane is correlated with open leads (cracks) in the sea ice and regions with fractional ice cover (Kort et al., 2012). In the recently published Nature Geoscience paper, the authors suggest that the methane derives from a previously under-recognised source, aerated surface ocean waters.
Eric Kort, who led the study, told MethaneNet that the finding was “unexpected”. He explained how the work came about. “The observations were made as part of the HIAPER Pole-to-Pole Observations (HIPPO) campaign, on which we made airborne observations from 67S to 85N. Our attention was drawn to the Arctic methane question by an observation made onboard the aircraft. We noticed that on many profiles, as we descended near the ice-ocean surface, our instruments recorded increases in methane, with no coincident increase in carbon monoxide. This feature piqued our curiosity, and led to the analysis presented in our paper.”
The data were collected using instruments mounted onboard the NSF/NCAR Gulfstream V. During the five flights, from January 2009 to April 2010, methane, carbon monoxide, ozone and water vapour concentrations were measured at heights ranging from 0.15 – 8.5 km. Using the ancillary gas measurements, the authors were able to rule out biomass burning and oil and gas industry operations as the methane source.
Initial estimates suggest a flux rate of 0.5 – 8.0 mg CH4 d-1 m-2 from this newly revealed source. The research prompts many questions. How might future changes in sea ice cover impact the fluxes? Is there a connection with other recently reported Arctic methane sources such as degradation of subsea permafrost on the eastern Siberian shelf. How exactly is this methane produced?
Eric Kort recognizes that more information is needed, saying to MethaneNet, “hopefully our work motivates further study on methane emissions from Arctic Ocean”.
Kort, E.A., Wofsy, S.C.,Daube, B.C., Diao, M., Elkins, J.W., Gao, R.S., Hintsta, E.J., Hurst, D.F., Jiminez, R., Moore, F.L., Spackman, J.R., and Zondlo, M.A. (2012), Atmospheric observations of Arctic Ocean methane emissions up to 82°N. Nature Geoscience, 5, 318-321.
Image of Arctic sea ice by Stefan Cook @ flickr.com