IMPACT OF OCEANIC SOURCES OF BIOGENIC SULFUR ON SULFATE AEROSOL CONCENTRATIONS AT MAWSON, ANTARCTICA

Sulphate is the dominant aerosol species in the Antarctic atmosphere 1,2 and an important constituent in Antarctic snow and ice 3. Various sources have been suggested for Antarctic non-sea-salt sulphate (n.s.s. SO4(2-)): volcanic emissions, stratospheric injection, pollutants transported from the low latitudes and biogenic dimethylsulphide (DMS) from the ocean 1,2. Although the oceanic source is now believed to be especially important, there has been no strong chemical evidence directly linking oceanic DMS with the Antarctic n.s.s. SO4(2-) concentrations. Here we present extended measurements from the Antarctic for both n.s.s. SO4(2-) and methanesulphonate (MSA), an oxidation product of DMS. Both species have a very strong seasonal cycle with a maximum in the austral summer; this cycle parallels that of the oceanic biogenic sulphur producers, thereby suggesting a strong link between the Antarctic atmospheric sulphur cycle and biological processes in the Southern Ocean.