Wind-dependence of DMS transfer velocity: Comparison of model with recent southern ocean observations

This study estimates air-sea gas exchange for dimethyl sulfide (DMS) and related compounds by suggesting an additional physio-chemical mechanism that occurs at high wind speeds for surface active molecules. As wind speeds increase and the degree of whitecapping increases, the nature of the surface ocean changes. For organic molecules the introduction of bubbles into the water may change the effective activity coefficient. This study describes a model wherein the effective solubility of DMS in seawater is enhanced by changes in the activity coefficient of DMS at a range of wind speeds. This change in the effective water-side fugacity of the compound will influence the Henry’s Law constant, H, and therefore air-sea gas exchange at high wind speeds. The model predictions compare well to recent field data in the Southern Ocean and support an attenuation of air-sea exchange for surface active organic molecules at wind speeds over 10 ms. Estimates for air-sea exchange of related DMS precursors and derivatives are also presented.