Large and unexpected enrichment in stratospheric ^(16)O^(13)C^(18)O and its meridional variation
Creators
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1.
Yale University
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2.
California Institute of Technology
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3.
University of California, Berkeley
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4.
University of Miami
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5.
National Center for Atmospheric Research
Abstract
The stratospheric CO_2 oxygen isotope budget is thought to be governed primarily by the O(1D)+CO_2 isotope exchange reaction. However, there is increasing evidence that other important physical processes may be occurring that standard isotopic tools have been unable to identify. Measuring the distribution of the exceedingly rare CO_2 isotopologue ^(16)O^(13)C^(18)O, in concert with ^(18)O and ^(17)O abundances, provides sensitivities to these additional processes and, thus, is a valuable test of current models. We identify a large and unexpected meridional variation in stratospheric 16O13C18O, observed as proportions in the polar vortex that are higher than in any naturally derived CO_2 sample to date. We show, through photochemical experiments, that lower ^(16)O^(13)C^(18)O proportions observed in the midlatitudes are determined primarily by the O(1D)+CO_2 isotope exchange reaction, which promotes a stochastic isotopologue distribution. In contrast, higher ^(16)O^(13)C^(18)O proportions in the polar vortex show correlations with long-lived stratospheric tracer and bulk isotope abundances opposite to those observed at midlatitudes and, thus, opposite to those easily explained by O(1D)+CO_2. We believe the most plausible explanation for this meridional variation is either an unrecognized isotopic fractionation associated with the mesospheric photochemistry of CO_2 or temperature-dependent isotopic exchange on polar stratospheric clouds. Unraveling the ultimate source of stratospheric ^(16)O^(13)C^(18)O enrichments may impose additional isotopic constraints on biosphere–atmosphere carbon exchange, biosphere productivity, and their respective responses to climate change.
Additional Information
© 2009 by the National Academy of Sciences. Edited by Mark H. Thiemens, University of California at San Diego, La Jolla, CA, and approved May 26, 2009 (received for review March 16, 2009). Published ahead of print June 29, 2009. This article is a PNAS Direct Submission. We thank R. Lueb for WAS/CWAS field support and Y. L. Yung, G. A. Blake, and P. O. Wennberg for manuscript comments. This work was supported by the Davidow Fund (California Institute of Technology), the National Science Foundation, the National Aeronautics and Space Administration Upper Atmosphere Research Program, and the Camille Dreyfus Teacher–Scholar Award (to K.A.B.). Author contributions: L.Y.Y., H.P.A., M.O., and J.M.E. designed research; L.Y.Y., H.P.A., K.J.H., W.G., E.L.A., S.M.S., and K.A.B. performed research; L.Y.Y., H.P.A., W.G., and A.A.W. performed modeling; L.Y.Y., H.P.A., K.J.H., A.A.W., K.A.B., and J.M.E. contributed new reagents/analytic tools; L.Y.Y., H.P.A., W.G., A.A.W., M.O., K.A.B., and J.M.E. analyzed data; and L.Y.Y., H.P.A., W.G., A.A.W., K.A.B., and J.M.E. wrote the paper. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/cgi/content/full/0902930106/DCSupplemental.Errata
Correction for Yeung et al., Large and unexpected enrichment in stratospheric 16O13C18O and its meridional variation Proceedings of the National Academy of Sciences Nov 2009, 106 (45) 19203; DOI: 10.1073/pnas.0911372106Attached Files
Published - Yeung2009p5128P_Natl_Acad_Sci_Usa.pdf
Supplemental Material - Yeung0902930106SI.pdf
Erratum - Yeung2009p6435P_Natl_Acad_Sci_Usa.pdf
Files
Yeung0902930106SI.pdf
Additional details
Identifiers
- PMCID
- PMC2710640
- Eprint ID
- 15253
- Resolver ID
- CaltechAUTHORS:20090821-152327642
Related works
- Describes
- 10.1073/pnas.0911372106 (DOI)
Funding
- Caltech Davidow Fund
- NSF
- NASA
- Camille and Henry Dreyfus Foundation
Dates
- Created
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2009-09-08Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field