Drivers of Atmospheric Volatile Methylated Sulfur Variability Across the Southern Ocean and Antarctic Coast

Abstract. Biogenic volatile methylated sulfur (VMS) gases, dimethyl sulfide (DMS) and methanethiol (MeSH), are major precursors of climate-cooling sulfate aerosol, yet their sources, co-emission and fate remain poorly constrained over the Southern Ocean and Antarctica. In this study, we combine atmospheric VMS measurements with biogeochemical and meteorological observations from an austral summer Southern Ocean voyage to examine the drivers of atmospheric VMS concentrations across contrasting ocean-atmosphere regimes. At the Antarctic Ice Edge (62–67° S), DMS dominated the VMS burden (up to 5.7 ppb) with episodic coastal polynya and shelf biological hotspots demonstrating very low MeSH:DMS (0.3–4 %). In this regime, DMS variability was strongly related to recent air mass exposure to high surface chlorophyll-a (R² = 0.49), whereas MeSH showed little dependence (R² < 0.14), consistent with stronger heterotrophic control on MeSH production. Over the open ocean (32–62° S), DMS and MeSH were tightly coupled (R² = 0.80) with higher MeSH (up to 250 ppt) and MeSH:DMS (~15 %), but chlorophyll-a explained little of the variability (R² = 0.15); instead, physical ocean structure and boundary-layer conditions influenced VMS variability. DMS and DMSO co-varied at the Antarctic Ice-Edge (R² = 0.69), indicating rapid oxidation via addition reactions with hydroxyl and bromine monoxide radicals at the surface. Overall, our results support developing coupled VMS-biogeochemical parameterisations to better capture aerosol-cloud representation in Southern Ocean climate models, and revising DMS-based parameterisations of MeSH at the Antarctic Ice-Edge, which currently appear to overestimate MeSH contributions to the VMS burden under these conditions.