P. Veres, J. Neuman, J. Neuman
Feb 18, 2020
Citations
5
Influential Citations
123
Citations
Quality indicators
Journal
Proceedings of the National Academy of Sciences
Abstract
Significance Dimethyl sulfide (DMS) has been the subject of a decades-long research effort due to its role as the major natural global sulfur emission. DMS oxidation across the world’s ocean basins is thought to produce sulfate aerosol, which in turn alters Earth’s albedo and climate. Details of the DMS oxidation mechanism are critical in defining this atmospheric chemistry–climate interaction. We present the atmospheric discovery and global in situ observations of a major DMS gas-phase oxidation product, hydroperoxymethyl thioformate (HPMTF). Inclusion of HPMTF in descriptions of DMS oxidation is essential in models addressing marine aerosol formation, growth, and global distributions of cloud condensation nuclei (CCN). These findings represent a major shift in the understanding of this important biogeochemical cycle. 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.