Air–sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

摘要

Shipboard measurements of eddy covariance dimethylsulfide (DMS) air–sea fluxes and seawaterconcentration were carried out in the North Atlantic bloom region inJune/July 2011. Gas transfer coefficients () show a lineardependence on mean horizontal wind speed at wind speeds up to 11 m s.At higher wind speeds the relationship between and wind speedweakens. At high winds, measured DMS fluxes were lower than predicted basedon the linear relationship between wind speed and interfacial stressextrapolated from low to intermediate wind speeds. In contrast, the transfercoefficient for sensible heat did not exhibit this effect. The apparentsuppression of air–sea gas flux at higher wind speeds appears to be relatedto sea state, as determined from shipboard wave measurements. Theseobservations are consistent with the idea that long waves suppressnear-surface water-side turbulence, and decrease interfacial gas transfer. Thiseffect may be more easily observed for DMS than for less soluble gases, suchas CO, because the air–sea exchange of DMS is controlled byinterfacial rather than bubble-mediated gas transfer under high wind speedconditions.