PRE2023- GOOSE: Gaps in the Observation of Ocean Sulfur Emission and its modeling - PID2022-140872NB-I00

Marine sulfur emissions have a recognized potential to regulate climate through their role in aerosol and cloud formation over the oceans. However, current Earth System Models struggle to simulate oceanic sulfur emissions, which results in unreliable projections of future emissions under global warming. This is mainly because significant production and removal pathways of volatile organosulfur compounds are missing from current conceptual and mechanistic models. Moreover, current models focus solely on dimethylsulfide (DMS), the most abundant sulfur volatile emitted by the ocean. Recent observations, however, have revealed that methanethiol (MeSH, a compound related to DMS yet hitherto ignored by models) can make a sizable contribution to marine sulfur emissions. The PhD candidate will address pressing knowledge gaps in the marine sulfur cycle through experimental studies, both in the laboratory and on oceanographic cruises. Incubations of seawater samples and microbial plankton cultures will be used to disentangle the role of microbial metabolism and abiotic processes (e.g. photochemistry) in the budgets of plankton-made sulfur volatiles and related compounds. Naturally occurring compounds and added tracers (labeled with stable isotopes) will be measured using a standard Gas Chromatograph-Mass Spectrometer (GC-MS) and also a Proton Transfer Reaction Time of Flight Mass Spectrometer (PTR-ToF-MS), which allows for highly sensitive continuous measurements.