Seasonal variations of dimethylsulfide emissions and atmospheric sulfur and nitrogen species over the western North Atlantic Ocean

The DMS flux from the open ocean ranged from 1.3 μmol/m²/d in winter to 5-10 μmol/m²/d in late summer and fall. The annual DMS flux from the WNAO area is estimated to be 0.1 Tg S/yr. SO₂ and nss-SO₄^2- concentrations varied strongly with wind direction. SO₂ levels were as low as 10 pptv in marine air and reached several ppbv in continentally derived air. Relatively weak and statistically not significant seasonal variations were observed for MSA, NO ^-₃, and MSA/nss-SO₄^2- and NO₃^-/nss-SO₄^2- ratios. In contrast, NH₄⁺ concentrations showed a clear seasonal variation with a maximum in late summer/early fall and a minimum in winter. Oceanic ammonia emissions may be important for marine background levels of ammonia and NH₄⁺ in the WNAO atmosphere. Aerosol particles were predominantly acidic with NH₄⁺/nss-SO₄^2- ratios of 1-2 mol/mol. -from Authors