Abstract. Oceanic emissions of dimethyl sulfide (CH3SCH3,DMS) have long been recognized to impact aerosol particle composition andsize, the concentration of cloud condensation nuclei (CCN), and Earth'sradiation balance. The impact of oceanic emissions of methanethiol(CH3SH, MeSH), which is produced by the same oceanic precursor as DMS,on the volatile sulfur budget of the marine atmosphere is largelyunconstrained. Here we present direct flux measurements of MeSH oceanicemissions using the eddy covariance (EC) method with a high-resolutionproton-transfer-reaction time-of-flight mass spectrometer (PTR-ToFMS)detector and compare them to simultaneous flux measurements of DMS emissionsfrom a coastal ocean site. Campaign mean mixing ratios of DMS and MeSH were72 ppt (28–90 ppt interquartile range) and 19.1 ppt (7.6–24.5 pptinterquartile range), respectively. Campaign mean emission fluxes of DMS (FDMS) and MeSH (FMeSH) were 1.13 ppt m s−1 (0.53–1.61 ppt m s−1 interquartile range) and 0.21 ppt m s−1 (0.10–0.31 ppt m s−1 interquartile range), respectively. Linear least squares regression of observed MeSH and DMS flux indicates the emissions are highly correlatedwith each other (R2=0.65) over the course of the campaign,consistent with a shared oceanic source. The campaign mean DMS to MeSH fluxratio (FDMS:FMeSH) was 5.5 ± 3.0, calculated from the ratio of 304 individual coincident measurements of FDMS and FMeSH. Measured FDMS:FMeSH was weakly correlated (R2=0.15) withocean chlorophyll concentrations, with FDMS:FMeSH reaching a maximumof 10.8 ± 4.4 during a phytoplankton bloommore »
Global airborne sampling reveals a previously unobserved dimethyl sulfide oxidation mechanism in the marine atmosphere
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, HOOCH 2 SCHO), 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.
- Authors:
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Award ID(s):
- 1801971
- Publication Date:
- NSF-PAR ID:
- 10150057
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 117
- Issue:
- 9
- Page Range or eLocation-ID:
- 4505 to 4510
- ISSN:
- 0027-8424
- Sponsoring Org:
- National Science Foundation
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