Fluxes of geochemically interesting gases typically rely on gas exchange models incorporating
measurements of gas concentration together with surface layer transport models. These bulk methods
rely on the assumption that the flux of a gas across an air-water interface is governed by the air-water
concentration difference and by the gas transfer velocity - essentially the hydrodynamics of the surface
water layer. The concentration difference is usually measurable in situ; parameterization of the transfer
velocity is not as easily accomplished in situ. The transfer velocity has also been estimated by bomb
14CO2, but the integration time for this measurement is years. Dual tracer injection studies and Rn
studies have brought the integration time down to days and weeks. The value of these longer term
averages for understanding gas exchange is limited since the physical processes controlling exchange
vary on much shorter time-scales. We used a profile technique to measure the flux of DMS in situ to
shorten flux integrations to scales of hours. Dimethylsulfide is supersaturated relative to atmospheric
concentrations virtually everywhere in surface ocean waters. The relatively short lifetime of DMS in the
atmosphere (days) keeps its atmospheric concentration low, thereby providing an opportunity to measure
DMS flux from the sea surface by measuring vertical profiles in the lower marine boundary layer. We
conducted profile measurements at Scripps Pier and from the bow of a ship during a CoOP cruise near
Martha's Vineyard to evaluate the DMS method. We also measured wind speed, humidity, air and sea
temperature to determine wind stress and atmospheric stability. DMS fluxes measured at Scripps Pier
and on Oceanus were similar (24.4 vs 23.7 µmolm-2day-1). The transfer velocity south of Martha's
Vineyard was considerably higher (44.2 cm/hr vs 7.7 cm/hr), in part because of the higher u* (0.25 msec-1 vs. 0.11-0.14 msec-1) while the DMS concentration in the water was lower.