The origin of methane in the East Siberian Arctic Shelf unraveled with triple isotope analysisстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Scopus,
Web of Science
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 20 марта 2018 г.
Аннотация: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.