THE EMISSION RATE OF DIMETHYL SULFIDE AT THE ATMOSPHERIC-OCEANIC INTERFACE

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Abstract
Dimethyl sulfide appears to be present everywhere in the surface ocean, is readily transferred into the marine atmosphere, and may account for about 30% of the natural component of the overall sulfur budget in the atmosphere. To investigate the apparent discrepancies between measured DMS fluxes, and theoretical predictions, we have examined the transport of DMS across the marine-atmosphere interface. An analysis of vertical flux was performed with a two-film model for the transport of DMS across the marine-atmosphere interface with chemical reactions. The photosensitized oxidation of DMS, its reaction with hydrogen peroxide in the aqueous film, and reactions with nitrate and hydroxyl radicals in the gas film have negligible effect on the DMS flux to the marine atmosphere. However, the flux of DMS into the atmosphere is most sensitive to the liquid-film thickness but not to changes in temperature and gas-film thickness. Model calculations showed that if the liquid-film thickness increases from 35 μm (turbulent sea conditions) to 200 μm (calm sea conditions), the flux of DMS reduces from 290 to 55 μg S m−2 day−1 at an ocean temperature of 15°C for a constant gas-film thickness of 0.3 cm