Methane concentration and isotopic composition was measured in ice-covered and ice-free waters of theArctic Ocean during 11 surveys spanning the years of 1992–1995 and 2009. During ice-free periods, methaneflux from the Beaufort shelf varies from 0.14 mg CH4 m22 d21 to 0.43 mg CH4 m22 d21. Maximum fluxesfrom localized areas of high methane concentration are up to 1.52 mg CH4 m22 d21. Seasonal buildup ofmethane under ice can produce short-term fluxes of methane from the Beaufort shelf that varies from0.28 mg CH4 m22 d21 to 1.01 mg CH4 m22 d21. Scaled-up estimates of minimum methane flux from theBeaufort Sea and pan-Arctic shelf for both ice-free and ice-covered periods range from 0.02 Tg CH4 yr21 and0.30 Tg CH4 yr21, respectively to maximum fluxes of 0.18 Tg CH4 yr21 and 2.2 Tg CH4 yr21, respectively. Amethane flux of 0.36 Tg CH4 yr21 from the deep Arctic Ocean was estimated using data from 1993 to 1994.The flux can be as much as 2.35 Tg CH4 yr21 estimated from maximum methane concentrations and windspeeds of 12 m/s, representing only 0.42% of the annual atmospheric methane budget of ? 560 Tg CH4 yr21.There were no significant changes in methane fluxes during the time period of this study. Microbial methanesources predominate with minor influxes from thermogenic methane offshore Prudhoe Bay and the MackenzieRiver delta and may include methane from gas hydrate. Methane oxidation is locally important on theshelf and is a methane sink in the deep Arctic Ocean.
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