Methane flux to the atmosphere from the Deepwater Horizon oil disaster

The sea‐to‐air flux of methane from the blowout at the Deepwater Horizon was measured with substantial spatial and temporal resolution over the course of seven days in June 2010. Air and water concentrations were analyzed continuously from a flowing air line and a continuously flowing seawater equilibrator using cavity ring‐down spectrometers (CRDS) and a gas chromatograph with a flame ionization detector (GC‐FID). The results indicate a low flux of methane to the atmosphere (0.024 μmol m−2 d−1) with atmospheric and seawater equilibrium mixing ratios averaging 1.86 ppm and 2.85 ppm, respectively within the survey area. The oil leak, which was estimated to contain 30.2% methane by weight, was not a significant source of methane to the atmosphere during this study. Most of the methane emitted from the wellhead was dissolved in the deep ocean.