{"@context":{"@vocab":"https://cir.nii.ac.jp/schema/1.0/","rdfs":"http://www.w3.org/2000/01/rdf-schema#","dc":"http://purl.org/dc/elements/1.1/","dcterms":"http://purl.org/dc/terms/","foaf":"http://xmlns.com/foaf/0.1/","prism":"http://prismstandard.org/namespaces/basic/2.0/","cinii":"http://ci.nii.ac.jp/ns/1.0/","datacite":"https://schema.datacite.org/meta/kernel-4/","ndl":"http://ndl.go.jp/dcndl/terms/","jpcoar":"https://github.com/JPCOAR/schema/blob/master/2.0/"},"@id":"https://cir.nii.ac.jp/crid/1361981469733324672.json","@type":"Article","productIdentifier":[{"identifier":{"@type":"DOI","@value":"10.1029/2007jc004217"}},{"identifier":{"@type":"URI","@value":"https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1029%2F2007JC004217"}},{"identifier":{"@type":"URI","@value":"https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2007JC004217"}}],"dc:title":[{"@value":"Carbon isotopic characterization for the origin of excess methane in subsurface seawater"}],"description":[{"type":"abstract","notation":[{"@value":"<jats:p>We collected samples of seawater, zooplankton, and sinking particles in the northwestern North Pacific to determine the source of excess CH<jats:sub>4</jats:sub> over the saturation value in equilibrium with the atmospheric CH<jats:sub>4</jats:sub> in the oxygenated open ocean, using stable carbon isotope as a tracer. We found that subsurface (∼100 m depth) seawater is supersaturated (up to 12%) with <jats:sup>13</jats:sup>C‐enriched CH<jats:sub>4</jats:sub> (up to −33.1‰) relative to surface seawater in equilibrium with the atmosphere (−47‰), suggesting that in situ addition of <jats:sup>13</jats:sup>C‐enriched CH<jats:sub>4</jats:sub> must be responsible for CH<jats:sub>4</jats:sub> enrichment at depth. The <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C of CH<jats:sub>4</jats:sub> emitted from sinking particles (from −36.7 ± 1.2‰ to +5.9 ± 7.5‰) is within the range of that of excess CH<jats:sub>4</jats:sub> in seawater, suggesting that the major source of subsurface excess CH<jats:sub>4</jats:sub> is sinking particles. The unusually <jats:sup>13</jats:sup>C‐enriched <jats:italic>δ</jats:italic><jats:sup>13</jats:sup>C composition of CH<jats:sub>4</jats:sub> emitted from sinking particles suggests that active microbial CH<jats:sub>4</jats:sub> oxidation occurs within the oxic/anoxic boundary of these particles. On the basis of the Rayleigh equation, we estimated that at least 62% of CH<jats:sub>4</jats:sub> produced within the anoxic center of sinking particles is oxidized within 100 m of the surface.</jats:p>"}]}],"creator":[{"@id":"https://cir.nii.ac.jp/crid/1381981469733324675","@type":"Researcher","foaf:name":[{"@value":"Motoki Sasakawa"}],"jpcoar:affiliationName":[{"@value":"Division of Earth and Planetary Sciences, Graduate School of Science Hokkaido University  Sapporo Japan"},{"@value":"Japan Society for the Promotion of Science  Tokyo Japan"}]},{"@id":"https://cir.nii.ac.jp/crid/1381981469733324676","@type":"Researcher","foaf:name":[{"@value":"Urumu Tsunogai"}],"jpcoar:affiliationName":[{"@value":"Division of Earth and Planetary Sciences, Graduate School of Science Hokkaido University  Sapporo Japan"}]},{"@id":"https://cir.nii.ac.jp/crid/1381981469733324673","@type":"Researcher","foaf:name":[{"@value":"Sohiko Kameyama"}],"jpcoar:affiliationName":[{"@value":"Division of Earth and Planetary Sciences, Graduate School of Science Hokkaido University  Sapporo Japan"},{"@value":"Japan Society for the Promotion of Science  Tokyo Japan"}]},{"@id":"https://cir.nii.ac.jp/crid/1381981469733324674","@type":"Researcher","foaf:name":[{"@value":"Fumiko Nakagawa"}],"jpcoar:affiliationName":[{"@value":"Division of Earth and Planetary Sciences, Graduate School of Science Hokkaido University  Sapporo Japan"}]},{"@id":"https://cir.nii.ac.jp/crid/1381981469733324672","@type":"Researcher","foaf:name":[{"@value":"Yukihiro Nojiri"}],"jpcoar:affiliationName":[{"@value":"National Institute for Environmental Studies  Ibaraki Japan"}]},{"@id":"https://cir.nii.ac.jp/crid/1381981469733324677","@type":"Researcher","foaf:name":[{"@value":"Atsushi Tsuda"}],"jpcoar:affiliationName":[{"@value":"Ocean Research Institute University of Tokyo  Tokyo Japan"}]}],"publication":{"publicationIdentifier":[{"@type":"PISSN","@value":"01480227"}],"prism:publicationName":[{"@value":"Journal of Geophysical 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