| Summary: | The East Siberian Arctic shelf (ESAS) is the largest (~10% of the world ocean shelf area) and the shallowest shelf (mean depth <50 m) of the world ocean. Until this study, the ESAS was not considered a source of methane (CH4) to the atmosphere due to subsea permafrost’s impermeability, which completely isolated it from modern biogeochemical cycles. The ESAS stores the world’s largest hydrocarbon stocks, mostly as shallow Arctic hydrates, and thus represents an enormous potential CH4 atmospheric source that could result from global warming-triggered permafrost degradation. Increased CH4 fluxes could occur as numerous weak seeps or strong bubble plumes over large areas. Due to the shallow nature of the ESAS, the majority of ESAS CH4 likely avoids oxidation and escapes to the atmosphere. To assess whether sudden, large-scale CH4 release occurs or is likely to occur in the future, we investigated spatial and temporal variability as well as the controlling factors of CH4 flux to the water column, and to the atmosphere. This data set contains results of CH4 measurements performed in the water column using headspace analysis (ppm in gaseous phase) during the expeditions 2009-2010 and observed mixing ratios of CH4 in the atmospheric boundary layer above the water surface (ppm).
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