Methane fluxes from the sea to the atmosphere across the Siberian shelf seas

The Laptev and East Siberian Seas have been proposed as a substantial source of methane (CH 4 ) to the atmosphere. During summer 2014, we made unique high‐resolution simultaneous measurements of CH 4 in the atmosphere above, and surface waters of, the Laptev and East Siberian Seas. Turbulence‐driven sea‐air fluxes along the ship's track were derived from these observations; an average diffusive flux of 2.99 mg m −2 d −1 was calculated for the Laptev Sea and for the ice‐free portions of the western East Siberian Sea, 3.80 mg m −2 d −1 . Although seafloor bubble plumes were observed at two locations in the study area, our calculations suggest that regionally, turbulence‐driven diffusive flux alone accounts for the observed atmospheric CH 4 enhancements, with only a local, limited role for bubble fluxes, in contrast to earlier reports. CH 4 in subice seawater in certain areas suggests that a short‐lived flux also occurs annually at ice‐out.