Articles | Volume 16, issue 17
Atmos. Chem. Phys., 16, 10847–10864, 2016
Atmos. Chem. Phys., 16, 10847–10864, 2016

Research article 01 Sep 2016

Research article | 01 Sep 2016

Sensitivity of modelled sulfate aerosol and its radiative effect on climate to ocean DMS concentration and air–sea flux

Jan-Erik Tesdal1,a, James R. Christian2,3, Adam H. Monahan1, and Knut von Salzen3 Jan-Erik Tesdal et al.
  • 1School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia, Canada
  • 2Fisheries and Oceans Canada, Sidney, British Columbia, Canada
  • 3Canadian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, British Columbia, Canada
  • anow at: Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA

Abstract. Dimethylsulfide (DMS) is a well-known marine trace gas that is emitted from the ocean and subsequently oxidizes to sulfate in the atmosphere. Sulfate aerosols in the atmosphere have direct and indirect effects on the amount of solar radiation reaching the Earth's surface. Thus, as a potential source of sulfate, ocean efflux of DMS needs to be accounted for in climate studies. Seawater concentration of DMS is highly variable in space and time, which in turn leads to high spatial and temporal variability in ocean DMS emissions. Because of sparse sampling (in both space and time), large uncertainties remain regarding ocean DMS concentration. In this study, we use an atmospheric general circulation model with explicit aerosol chemistry (CanAM4.1) and several climatologies of surface ocean DMS concentration to assess uncertainties about the climate impact of ocean DMS efflux. Despite substantial variation in the spatial pattern and seasonal evolution of simulated DMS fluxes, the global-mean radiative effect of sulfate is approximately linearly proportional to the global-mean surface flux of DMS; the spatial and temporal distribution of ocean DMS efflux has only a minor effect on the global radiation budget. The effect of the spatial structure, however, generates statistically significant changes in the global-mean concentrations of some aerosol species. The effect of seasonality on the net radiative effect is larger than that of spatial distribution and is significant at global scale.

Short summary
A global atmosphere model with explicit representation of aerosol processes is used to assess uncertainties in the climate impact of ocean DMS efflux and the role of spatial and temporal variability of the DMS flux in the effect on climate. The radiative effect of sulfate is nearly linearly related to global total DMS flux. Removing the spatial or temporal variability of DMS flux changes the global radiation budget, but the effect is of second-order importance relative to the global mean flux.
Final-revised paper