Ocean Outgassing of Methyl Chloroform as an Underestimated Source of Emission
Name
Geophysical Research Letters - 2025 - Wang - Ocean Outgassing of Methyl Chloroform as an Underestimated Source of Emission.pdf
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Published version
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4.75 MB
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Author(s)
Wang, Peidong
Solomon, Susan
Scott, Jeffery R
Yvon‐Lewis, Shari A
Wennberg, Paul O
Weiss, Ray F
Rigby, Matthew
An, Minde
Date Issued
December 20, 2025
Journal
Geophysical Research Letters
Publisher
American Geophysical Union
Citation
Wang, P., Solomon, S., Scott, J. R., Yvon-Lewis, S. A., Wennberg, P. O., Weiss, R. F., et al. (2025). Ocean outgassing of methyl chloroform as an underestimated source of emission. Geophysical Research Letters, 52, e2025GL118618.
Version
Final published version
Abstract
Methyl chloroform (MCF) is an ozone‐depleting substance used as an industrial solvent. Itsprimary sink is oxidation by the hydroxyl radical (OH), making it a key tracer for estimating atmosphericoxidative capacity. Following Montreal Protocol regulations, MCF emissions declined rapidly after the 1990s.However, the recent atmospheric MCF decay suggests persistent emissions and/or declining OH (contradictingchemistry‐climate models projecting increasing or stable OH). The air‐sea exchange of MCF has been poorlyconstrained due to limited observations and simplified ocean representations. We simulate oceanic MCF fluxesusing a modern ocean reanalysis and validate with depth‐resolved observations. Results suggest the ocean hasshifted from a net sink to a net source around 2005, outgassing 0.5 Gg yr 1 in the 2010s (up to 30% of inferredMCF emissions). This ocean outgassing is an order of magnitude larger than previous estimates, and accountsfor up to a third of the model‐observation discrepancy in OH.
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DOI of Published Version
https://doi.org/10.1029/2025GL118618
