Abstract
Abstract. 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 the greater ice-free sea surface and higher biological activity. We implemented DMS(g) in the Environment and Climate Change Canada’s (ECCC) online air quality forecast model, GEM-MACH (Global Environmental Multiscale–Modelling Air quality and CHemistry), and compared model simulations with DMS(g) measurements made in Baffin Bay and the Canadian Arctic Archipelago in July and August 2014. Two seawater DMS(aq) datasets were used as input for the simulations: (1) a DMS(aq) climatology dataset based on seawater concentration measurements (Lana et al., 2011) and (2) a DMS(aq) dataset based on satellite detection (Galí et al., 2018). In general, GEM-MACH simulations under-predict DMS(g) measurements, which is likely due to the negative biases in both DMS(aq) datasets. However, a higher correlation and smaller bias were obtained with the satellite dataset. Agreement with the observations improved when climatological values were replaced by DMS(aq) in situ values that were measured concurrently with atmospheric observations over Baffin Bay and the Lancaster Sound area in July 2014. The addition of DMS(g) to the GEM-MACH model resulted in a significant increase in atmospheric SO2 for some regions of 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 the formation and growth of biogenic aerosol at high latitudes (>70∘ N). The enhancement in sulfate particles is most significant in the size range from 50 to 100 nm; however, this enhancement is stronger in the 200–1000 nm size range at lower latitudes (<70∘ N). These results emphasize the important role of DMS(g) in the formation and growth of fine and ultrafine sulfate-containing particles in the Arctic during the summertime.
Highlights
Atmospheric aerosol plays a crucial role in climate change
This general distribution pattern is consistent with the findings of Sharma et al (1999) from measurements taken on an expedition circumnavigating North America, including an Arctic Ocean transect in summer/fall 1994; they observed the highest dimethyl sulfide (DMS)(g) concentrations over the open waters of the Bering Sea south of the ice edge on the west side of the Arctic Ocean, whereas lower concentrations were observed on the Atlantic side (e.g. 5–10 nmol m−3, or ∼ 100–200 pptv over Labrador Sea)
The two simulations do differ on a local scale, e.g. higher DMS(g) mean mixing ratio values are evident in the figure using the SAT DMS(aq) dataset for some regions such as Hudson Bay and the Canadian Arctic Archipelago
Summary
Atmospheric aerosol plays a crucial role in climate change. Aerosol particles influence climate by absorption/scattering of short-/long-wave radiation (direct effect) and by changing the number/size of cloud droplets and altering precipitation efficiency (indirect effect) (e.g. Haywood and Boucher, 2000). Recent atmospheric observation and modelling studies suggest a significant role for DMS(g) in particle formation above oceans, especially in remote areas such as the Arctic during summer when anthropogenic aerosols are scarce and the condensation sink is low (Abbatt et al, 2019; Croft et al, 2019; Leaitch et al, 2013; Ghahremaninezhad et al, 2016; Burkart et al, 2017; Collins et al, 2017; Quinn et al, 2017).
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