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dc.contributor.authorRhodes, Rachaelen
dc.contributor.authorFaïn, Xen
dc.contributor.authorBrook, EJen
dc.contributor.authorMcConnell, JRen
dc.contributor.authorMaselli, OJen
dc.contributor.authorSigl, Men
dc.contributor.authorEdwards, Jen
dc.contributor.authorBuizert, Cen
dc.contributor.authorBlunier, Ten
dc.contributor.authorChappellaz, Jen
dc.contributor.authorFreitag, Jen
dc.date.accessioned2017-05-02T14:44:28Z
dc.date.available2017-05-02T14:44:28Z
dc.date.issued2016-04-26en
dc.identifier.issn1814-9324
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/263956
dc.description.abstractAdvances in trace gas analysis allow localised, non-atmospheric features to be resolved in ice cores, superimposed on the coherent atmospheric signal. These high-frequency signals could not have survived the low-pass filter effect that gas diffusion in the firn exerts on the atmospheric history and therefore do not result from changes in the atmospheric composition at the ice sheet surface. Using continuous methane (CH$_{4}$) records obtained from five polar ice cores, we characterise these non-atmospheric signals and explore their origin. Isolated samples, enriched in CH$_{4}$ in the Tunu13 (Greenland) record are linked to the presence of melt layers. Melting can enrich the methane concentration due to a solubility effect, but we find that an additional in situ process is required to generate the full magnitude of these anomalies. Furthermore, in all the ice cores studied there is evidence of reproducible, decimetre-scale CH$_{4}$ variability. Through a series of tests, we demonstrate that this is an artifact of layered bubble trapping in a heterogeneous-density firn column; we use the term "trapping signal" for this phenomenon. The peak-to-peak amplitude of the trapping signal is typically 5 ppb, but may exceed 40 ppb. Signal magnitude increases with atmospheric CH$_{4}$ growth rate and seasonal density contrast, and decreases with accumulation rate. Significant annual periodicity is present in the CH$_{4}$ variability of two Greenland ice cores, suggesting that layered gas trapping at these sites is controlled by regular, seasonal variations in the physical properties of the firn. Future analytical campaigns should anticipate high-frequency artifacts at high-melt ice core sites or during time periods with high atmospheric CH$_{4}$ growth rate in order to avoid misinterpretation of such features as past changes in atmospheric composition.
dc.description.sponsorshipPlease visit the publisher's website.
dc.languageengen
dc.language.isoenen
dc.publisherCopernicus Publications
dc.rightsAttribution 4.0 Internationalen
dc.rightsAttribution 4.0 Internationalen
dc.rightsAttribution 4.0 Internationalen
dc.rightsAttribution 4.0 Internationalen
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en
dc.titleLocal artifacts in ice core methane records caused by layered bubble trapping and in situ production: A multi-site investigationen
dc.typeArticle
prism.endingPage1077
prism.issueIdentifier4en
prism.publicationDate2016en
prism.publicationNameClimate of the Pasten
prism.startingPage1061
prism.volume12en
dc.identifier.doi10.17863/CAM.9332
dcterms.dateAccepted2016-04-19en
rioxxterms.versionofrecord10.5194/cp-12-1061-2016en
rioxxterms.versionVoRen
rioxxterms.licenseref.urihttp://creativecommons.org/licenses/by/4.0/en
rioxxterms.licenseref.startdate2016-04-26en
dc.contributor.orcidRhodes, Rachael [0000-0001-7511-1969]
dc.identifier.eissn1814-9332
rioxxterms.typeJournal Article/Reviewen


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Attribution 4.0 International
Except where otherwise noted, this item's licence is described as Attribution 4.0 International