DIMETHYL SULFIDE IN THE ARCTIC ATMOSPHERE

Dimethyl sulfide (DMS), sulfur dioxide, non-sea-salt sulfate, and vari ous aerosol properties were measured during three field programs (two airborne and one ground-based) near Barrow and Deadhorse (Prudhoe Bay) , Alaska. The two airborne sampling programs took place in spring and early summer, and the ground-based measurements spanned an entire summ er. DMS concentrations in the Arctic atmosphere ranged from a few part s per trillion by volume (pptv) in spring and fall to higher values in summer (generally a few tens of pptv with occasional peaks of 100 to 300 pptv). In addition, DMS concentrations were measured during the sp ring near Resolute in seawater below the ice and in ice-algae and kelp cultures. The seawater samples taken from below the ice in spring had DMS concentrations comparable to those in other oceanic regions. Take n together, these measurements show that the Arctic Ocean is potential ly a substantial source of DMS, which likely becomes important as sea ice melts in the early summer. Local atmospheric concentrations increa sed throughout the summer, peaking in August. In regions where accumul ation mode aerosols have been scavenged (e.g., by low-level stratus cl ouds, which are common during the Arctic summer), evidence of rapid ne w particle production was observed. The seasonal cycle of atmospheric DMS closely resembles that of fine particles observed at Barrow, Alask a, and Alert, Northwest Territories, Canada. This finding indicates th at DMS is likely an important precursor to the types of particles that dominate the background arctic aerosol in summertime. These results, together with those from several recently published studies of arctic aerosol, are combined to yield a consistent picture of the role of loc ally emitted DMS in the production of atmospheric aerosols in the Arct ic in summer.