Export fluxes of dimethylsulfoniopropionate and its break down gases at the air-sea interface

Abstract

Dimethylsulfide (DMS) results from the decomposition of dimethylsulfoniopropionate (DMSP), a biogenic product, in seawater. Diffusive transfer of DMS from sea-to-air is known to be the most important source of natural non- seasalt sulfur (NSS) in the atmosphere. Here, we report on the wider occurrence of DMSP in marine aerosols for the first time. We found DMSP (to about 4.7 pmol m^-3) and DMS (up to 5.8 pmol m^-3) in marine aerosols, over the Indian Ocean, wherein DMSP abundance appears to be a function of its concentration in surface seawater and wind speeds. An experiment on board revealed rapid loss (90%) of loaded DMSP from filters exposed to marine atmosphere. Hence, a photochemical or other mode of formation of NSS gases from DMSP in aerosols or in surface microlayer, not considered hitherto, can directly contribute to sulfur efflux. Although our computations suggest the DMSP fluxes from these sources to be much smaller (3.4 × 1010 g S y^-1) compared to DMS diffusive flux (16-25 × 1012 g S y^-1) the former could be significant in rough weather conditions similar to trends in water export.