Water‐air flux of dimethylsulfide

Abstract

The water‐air exchange of dimethylsulfide (DMS) has been measured in a laboratory wind‐wave tank in fresh and seawater. To understand the transport behavior of DMS, its exchange was measured simultaneously with that of O2, SF6, Ne, CH4, and He under varying wind speeds and hydrodynamic conditions. No unpredictable differences between fresh and seawater were found, indicating that DMS surface affinities do not exist in seawater. Results also indicate that Schmidt number corrections can be applied to DMS gas exchange. While the rate of transfer of relatively insoluble or sparingly soluble permanent gases between the ocean and the atmosphere is primarily controlled by the rate of flux through the aqueous boundary layer, interfacial mass balances indicate that increased DMS solubility increases the significance of the airside control of flux. The hypothesis that DMS transport across the water‐air interface is subject to waterside control for moderate environmental conditions is supported. However, for ocean‐atmospheric DMS exchange with low sea surface temperature or moderate wind speeds, there may be a significant influence by the atmospheric mass boundary layer. An atmospheric gradient fraction γa applied to the waterside air‐sea gas transfer velocity will correct for these effects. Estimates of ocean‐atmospheric DMS transfer velocities for these conditions are provided.