Methane emission from high-intensity marine gas seeps in the Black Sea into the atmosphere

Submarine high-intensity methane seeps have been surveyed in the Sorokin Trough and Paleo Dnepr Area in the Black Sea from May to June, 2003 to estimate the sea-air methane flux. The Sorokin Trough mud volcano area in around 2080 m water depth shows no direct effects on the methane concentration in the surface water and the atmosphere ( average methane saturation ratios (SR) of 143%). The average sea-air methane flux can be determined as 0.2 - 0.57 nmol m(-2) s(-1), using two different sea-air gas exchange models; mean wind speed were extraordinary low throughout the cruise ( 1.16 m s(-1)). The investigations in the Paleo Dnepr Area ( 60 to 800 m water depth) reflects a more diverse pattern. Spots of high methane concentrations in the surface water have been recorded above a seep location in around 90 m water depth ( SR up to 294%). The air-sea methane flux above this seep site (0.96 - 2.32 nmol m(-2) s(-1)) is 3 times higher than calculated for the surrounding shelf (0.32 - 0.77 nmol m(-2) s(-1)) and 5 times higher than assessed for open Black Sea waters ( water depth > 200 m, 0.19 - 0.47 nmol m(-2) s(-1)).