Dimethyl sulfide and its role in aerosol formation and growth in the Arctic summer – a modelling study

Abstract

<p><strong>Abstract.</strong> Atmospheric dimethyl sulfide, DMS(g), is a climatically important sulfur compound and is the main source of biogenic sulfate aerosol in the Arctic atmosphere. DMS(g) production and emission to the atmosphere increase during the summer due to greater ice-free sea surface and higher biological activity. We implemented DMS(g) in the GEM-MACH model (GEM: Global Environmental Multiscale – Environment and Climate Change Canada's (ECCC) numerical weather forecast model, MACH: ECCC's Modelling Air quality and CHemistry – chemistry and aerosol microphysics) for the Arctic region, and compared model simulations with DMS(g) measurements made in Baffin Bay and the Canadian Arctic Archipelago in July and August 2014. Two sea water DMS(aq) datasets were used as input to the simulations: (1) DMS(aq) climatology dataset based on seawater concentration measurements (Lana et al., 2011) and (2) DMS(aq) dataset based on satellite detection (Galí et al., 2018). In general, GEM-MACH simulations underpredict DMS(g) measurements, likely due to negative biases in both DMS(aq) datasets. Yet, higher correlation and smaller bias were obtained with the satellite dataset. Agreement with the observations improved by replacing climatological values with in situ measured DMS(aq) concurrently with atmospheric observations over Baffin Bay and Lancaster Sound area in July 2014.</p><p> The addition of DMS(g) to the GEM-MACH model resulted in a significant increase in atmospheric SO<sub>2</sub> for some regions in the Canadian Arctic (up to 100 %). Analysis of the size-segregated sulfate aerosol in the model shows that a significant increase in sulfate mass occurs for particles with a diameter smaller than 200 nm due to formation and growth of biogenic aerosol at high latitudes (> 70° N). The enhancement in sulfate particles is most significant in the size range of 50 to 100 nm, however, this enhancement is stronger in the 200–1000 nm size range at lower latitudes (< 70° N). These results emphasise the important role of DMS(g) in the formation and growth of fine and ultrafine sulfate-containing particles in the Arctic during the month of July.</p>