Regional and seasonal variations in the flux of oceanic dimethylsulfide to the atmosphere

Abstract

Dimethylsulfide (DMS) concentrations have been measured in over 1000 Pacific surface seawater samples during the past 4 years. The data have been tabulated to take into account both regional and seasonal variations in concentration. The area‐weighted summer and winter concentrations of DMS in the North Pacific Ocean are 2.2 and 1.3 nmol/L, respectively. Wind speed, surface seawater temperature, and DMS diffusivities are used to calculate air‐sea exchange coefficients. The area‐weighted summer and winter DMS piston velocities are 2.3 and 2.7 m/d, respectively. These exchange coefficients combined with the concentration data yield a net ocean to atmosphere DMS flux in the North Pacific Ocean of 0.12 Tmol/yr. Extrapolating this calculation by regional areas to the global ocean yields a net DMS flux of 0.50 Tmol/yr, less than earlier estimates of 1.2 Tmol/yr, but still consistent with excess sulfate deposition estimates and model studies of the marine atmospheric sulfur budget. The uncertainty in the flux estimate is roughly a factor of 2.