1Department of Chemistry, University of York, Heslington, York, YO19 4RR, UK
2British Antarctic Survey, High Cross, Madingley Road, CB3 0ET, Cambridge, UK
3Earth and Space Science Division, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
4School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
5Department of Chemistry, University of Leeds, Leeds LS2 9JT, UK
Abstract. In situ measurements of dimethyl sulphide (DMS) and methane sulphonic acid (MSA) were made at Halley Station, Antarctica (75°35´S, 26°19W) during February 2004–February 2005 as part of the CHABLIS (Chemistry of the Antarctic boundary layer and the interface with snow) project. DMS was present in the atmosphere at Halley all year (average 38.1±43 pptV) with a maximum monthly average value of 113.6±52 pptV in February 2004 coinciding temporally with a minimum in sea extent. Whilst seasonal variability and interannual variability can be attributed to a number of factors, short term variability appeared strongly dependent on air mass origin and trajectory pressure height. The MSA and derived non-sea salt sulphate (nss-SO42−) measurements showed no correlation with those of DMS (regression R2=0.039, and R2=0.001, respectively) in-line with the complexity of DMS fluxes, conflicting oxidation routes, transport of air masses and variable spatial coverage of both sea-ice and phytoplankton. MSA was generally low throughout the year, with an annual average of 42 ng m−3 (9.8±13.2 pptV), however MSA: nss-SO42− ratios were high implying a dominance of the addition oxidation route for DMS. Including BrO measurements into MSA production calculations demonstrated the significance of BrO on DMS oxidation within this region of the atmosphere in austral summer. Assuming an 80% yield of DMSO from the reaction of DMS+BrO, an atmospheric concentration of BrO equal to 3 pptV increased the calculated MSA production from DMS by a factor of 9 above that obtained when considering only reaction with the hydroxyl radical.