The origin of methane in the East Siberian Arctic Shelf unraveled with triple isotope analysis

Sapart, Célia J.; Shakhova, Natalia; Semiletov, Igor; Jansen, Joachim; Szidat, Sönke; Kosmach, Denis; Dudarev, Oleg; van der Veen, Carina; Egger, Matthias; Sergienko, Valentine; Salyuk, Anatoly; Tumskoy, Vladimir; Tison, Jean-Louis; Röckmann, Thomas (2017). The origin of methane in the East Siberian Arctic Shelf unraveled with triple isotope analysis. Biogeosciences, 14(9), pp. 2283-2292. European Geosciences Union 10.5194/bg-14-2283-2017

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The Arctic Ocean, especially the East Siberian Arctic Shelf (ESAS), has been proposed as a significant source of methane that might play an increasingly important role in the future. However, the underlying processes of formation, removal and transport associated with such emissions are to date strongly debated. CH4 concentration and triple isotope composition were analyzed on gas extracted from sediment and water sampled at numerous locations on the shallow ESAS from 2007 to 2013. We find high concentrations (up to 500 μM) of CH4 in the pore water of the partially thawed subsea permafrost of this region. For all sediment cores, both hydrogen and carbon isotope data reveal the predominant occurrence of CH4 that is not of thermogenic origin as it has long been thought, but resultant from microbial CH4 formation. At some locations, meltwater from buried meteoric ice and/or old organic matter preserved in the subsea permafrost were used as substrates. Radiocarbon data demonstrate that the CH4 present in the ESAS sediment is of Pleistocene age or older, but a small contribution of highly 14C-enriched CH4, from unknown origin, prohibits precise age determination for one sediment core and in the water column. Our sediment data suggest that at locations where bubble plumes have been observed, CH4 can escape anaerobic oxidation in the surface sediment.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)

UniBE Contributor:

Szidat, Sönke

Subjects:

500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry

ISSN:

1726-4189

Publisher:

European Geosciences Union

Language:

English

Submitter:

Sönke Szidat

Date Deposited:

06 Jun 2017 11:16

Last Modified:

11 Sep 2017 19:26

Publisher DOI:

10.5194/bg-14-2283-2017

BORIS DOI:

10.7892/boris.100942

URI:

https://boris.unibe.ch/id/eprint/100942

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