| Summary: | We present eddy covariance based CO2 and DMS fluxes and gas exchange coefficients (piston velocities) measured in situ during a 10-day cruise in the North Atlantic during summer 2007. Most current parameterizations of air/sea gas exchange utilize a generalized piston velocity, k, which relates the gas flux to the air/sea concentration difference, and incorporates all the physical factors controlling gas transport through both sides of the air/sea interface. Tracer release studies have shown that k increases with wind speed, though the functional form of the wind speed-dependence has not been well constrained due to averaging of flux estimates over varying environmental conditions, and also likely due to processes affecting gas exchange that are not correlated to wind speed. During the past decade, the micrometeorological technique eddy covariance (EC) has been used from ships at sea to measure k on short temporal and spatial scales, allowing for measurement of a wide range of environmental conditions on a single expedition. EC- based studies of CO2 and DMS in the Atlantic and Pacific Oceans have clearly shown wind speed dependency of k; however, a wide range of functional relationships is found among the cruises data sets. These differences may reflect differences in physical forcing of gas exchange in different environments, differing behavior of DMS versus CO2 due to solubility, or perhaps methodological differences. The simultaneous measurement of gas transfer coefficients of CO2 and DMS can provide insight into the sensitivity of gas exchange to gas solubility, and the extent to which gas transfer coefficients can be estimated from similarity relationships
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