Biological process in the surface ocean may contribute significantly to the composition of the overlying atmosphere, though direct emission of bacteria, viruses and algal debris, and through emission of reactive volatile organic compounds (VOCs) including dimethyl sulfide. The SOAP (Surface Ocean Aerosol Production) voyage in February 2012 examined biological influences on aerosol production and chemical composition east of New Zealand, by targeting phytoplankton blooms along the Sub-Tropical Front along Chatham Rise in the South West Pacific. We present atmospheric concentrations of dimethyl sulfide (DMS), methanethiol (MeSH) and acetone in the atmosphere, measured continuously during the voyage using a Proton Transfer Reaction Mass Spectrometer.
DMS and MeSH atmospheric concentrations correlated throughout the voyage, and diurnal cycles of DMS and MeSH show similar behaviour with the lowest concentration in mid-afternoon, likely due to photochemical destruction. The DMS diurnal cycle shows similar behaviour to historical published DMS measurements at Cape Grim, Tasmania, but with higher concentrations (factor of 2-4 times higher). Acetone and DMS atmospheric concentrations correlated during Bloom 1 which had very high concentrations of water and atmospheric DMS.
Ocean sources of atmospheric DMS, MeSH and acetone are explored by correlating atmospheric measurements with seawater biogeochemical parameters. Finally, the MeSH sea-air flux during the voyage is estimated.