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Dimethyl sulfide (DMS), emitted from the oceans, is the most abundant biological source of sulfur to the marine atmosphere. Atmospheric DMS is oxidized to condensable products that form secondary aerosols that affect Earth’s radiative balance by scattering solar radiation and serving as cloud condensation nuclei. We report the atmospheric discovery of a previously unquantified DMS oxidation product, hydroperoxymethyl thioformate (HPMTF, HOOCH2SCHO), identified through global-scale airborne observations that demonstrate it to be a major reservoir of marine sulfur. Observationally constrained model results show that more than 30% of oceanic DMS emitted to the atmosphere forms HPMTF. Coincident particle measurements suggest a strong link between HPMTF concentration and new particle formation and growth. Analyses of these observations show that HPMTF chemistry must be included in atmospheric models to improve representation of key linkages between the biogeochemistry of the ocean, marine aerosol formation and growth, and their combined effects on climate.
Additional National Oceanic and Atmospheric Administration (NOAA) support for ATom was provided by NASA funding via Inter-Agency Transfer NNH15AB12l and by funding from the NOAA Climate Program Office and the NOAA Atmospheric Chemistry, Carbon Cycle, and Climate program. K.H.M. and H.G.K. acknowledge the financial support of the Independent Research Fund Denmark, the University of Copenhagen, and the Danish Ministry for Higher Education and Science’s Elite Research travel grant. J.L.J.’s group acknowledges NASA grants NHX15AH33A and 80NSSC19K0124. A.K. was supported by the Austrian Science Fund’s Erwin Schrodinger Fellowship. A.S.-L., Q.L., and C.A.C. are supported by the European Research Council (ERC) Executive Agency under the European Union’s Horizon 2020 Research and Innovation programme (Project ERC-2016-COG 726349 CLIMAHAL). The National Center for Atmospheric Research is sponsored by the National Science Foundation. E.A. and J.B. were funded in part by NASA Atmospheric Composition Program. T.H.B. and C.M.J. acknowledge support from the National Science Foundation Center for Aerosol Impacts on Chemistry of the Environment under grant CHE 1801971. B.W. and M.D. have received funding from the ERC under the European Union’s Horizon 2020 research and innovation framework program under grant 640458 (A-LIFE) and from the University of Vienna.