A model of DMS emission in the western north Atlantic
Résumé
Dimethylsulfide (DMS) is produced in the oceanic surface layer by biological processes and is the major volatile organic sulfur compound entering the atmosphere. It is suspected to partly counteract greenhouse warming because of its contribution to aerosol formation. Current climate models use empirical relationships between surface DMS concentrations and surface temperature to estimate fluxes of DMS to the atmosphere. This approach is limiting in terms of the study of potential climate feedbacks via biological activity. We are developing a model of the biological processes involved in DMS production (NODEM for Northern Ocean DMS Emission Model). Our objectives are to: (1) provide improved representations of biologically-mediated DMS emission for a climate model that includes the effect of aerosols on the radiative balance (NARCM), and (2) investigate the sensitivity of DMS emissions to climate change scenarios. The model simulates complex interactions including the production and senescence of DMSP (dimethylsufoniopropionate, the precursor of DMS) phytoplankton carriers, zooplankton grazing, microbial processes, photo-oxidation and ventilation. The development of the model relies on experimental and in situ mesurements of DMS and DMSP collected during NODEM cruises in May-June 1997 and 1998. Remote sensing images of ocean color will be used to initialize the model and to compare with fluxes measured at selected stations. The model will then be incorporated in a one-dimensional version of NARCM (LCM) to allow initialisation from atmospheric simulations and to study the sensitivity of DMS fluxes to climate change.