Through the Cracks: Sea Ice Regions as a Source of Volatile Marine Sulfur in the Springtime Arctic

Marine volatile methylated sulfur compounds (VMS) including dimethyl sulfide (DMS) and methanethiol (MeSH), are important natural sources of sulfur to the atmosphere and precursors to aerosols and cloud condensation nuclei. However, observations of DMS and MeSH in regions with sea ice remain limited. We present VMS measurements in the Arctic springtime from the ARTofMELT expedition. Hourly averaged DMS and MeSH observations range from below detection limit (<1 ppt v ) to >1500 ppt v , and from below detection limit (<0.5 ppt v ) to >150 ppt v respectively, with the highest concentrations observed during open ocean influence. MeSH made an important contribution to Arctic atmospheric VMS (median MeSH:DMS ratio of 0.12). In regional atmospheric chemistry model simulations using an oceanic DMS climatology and no sea‐to‐air flux from grid cells with sea ice concentration (SIC) > 0, the DMS log 10 mean bias (LMB) is −0.82 with a mean bias (MB) of −101 ppt v ; the MeSH LMB is −0.81 (MB = −3 ppt v ). Scaling the sea‐to‐air flux by ocean fraction improves the atmospheric VMS model‐observation agreement by better representing VMS emissions during ocean influence from sea‐ice regions. Simulations which scale sea‐to‐air flux by ocean fraction and use different oceanic DMS data sets: the Lana climatology, a machine learning model, and a sea‐ice‐ocean‐biogeochemistry model, have a DMS LMB of 0.22, −0.49, and 0.02, respectively. These analyses provide evidence that MeSH is an important fraction of atmospheric VMS and both partial‐sea‐ice and open‐ocean regions are sources of marine sulfur to the atmosphere in the late‐springtime Arctic, both must be considered in atmospheric models.