Biotic and abiotic factors controlling isoprene, DMS, and oxygenated volatile organic compounds (VOCs) at the Southern Ocean in the Austral fall

We present shipborne observations of volatile organic compounds such as dimethylsulfide (DMS), isoprene, acetaldehyde, acetone, and methanol over the Southern Ocean in April and May 2018. During the cruise, we encountered air masses influenced by the open ocean, coastal Antarctica, and sea ice. No direct correlation between oceanographic parameters and ambient distributions of VOCs is found. Nonetheless, the previously reported correlations among the observed VOCs are found in our observed dataset. The statistically meaningful (R² > 0.2) anti-correlation of DMS with acetone and methanol is consistent with the previous report about biological activities associated with DMS emission and uptake of methanol and acetone. A positive correlation for isoprene and acetaldehyde, notably in the air masses originating from coastal Antarctica, indicates that photolysis of dissolved organic matter (DOM) was the likely source for the compounds when we conducted the observations. In addition, the observed VOCs were often enhanced over the sea ice observations. This can be accounted for by the ventilation processes of the dissolved VOCs under the ice.