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Large and unexpected enrichment in stratospheric ^(16)O^(13)C^(18)O and its meridional variation

Yeung, Laurence Y. and Affek, Hagit P. and Hoag, Katherine J. and Guo, Weifu and Wiegel, Aaron A. and Atlas, Elliot L. and Schauffler, Sue M. and Okumura, Mitchio and Boering, Kristie A. and Eiler, John M. (2009) Large and unexpected enrichment in stratospheric ^(16)O^(13)C^(18)O and its meridional variation. Proceedings of the National Academy of Sciences of the United States of America, 106 (28). pp. 11496-11501. ISSN 0027-8424. PMCID PMC2710640.

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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.

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URLURL TypeDescription CentralArticle ErrataCorrection Information
Atlas, Elliot L.0000-0003-3847-5346
Okumura, Mitchio0000-0001-6874-1137
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
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.0911372106
Funding AgencyGrant Number
Caltech Davidow FundUNSPECIFIED
Camille and Henry Dreyfus FoundationUNSPECIFIED
Subject Keywords:clumped isotopes; CO2; mesosphere; polar vortex; stratosphere
Issue or Number:28
PubMed Central ID:PMC2710640
Record Number:CaltechAUTHORS:20090821-152327642
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Official Citation:Laurence Y. Yeung, Hagit P. Affek, Katherine J. Hoag, Weifu Guo, Aaron A. Wiegel, Elliot L. Atlas, Sue M. Schauffler, Mitchio Okumura, Kristie A. Boering, and John M. Eiler Large and unexpected enrichment in stratospheric 16O13C18O and its meridional variation PNAS 2009 106 (28) 11496-11501; published ahead of print June 29, 2009, doi:10.1073/pnas.0902930106
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15253
Deposited By: George Porter
Deposited On:08 Sep 2009 19:17
Last Modified:04 May 2020 18:44

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