{"NOAAStudyId":"12256","contactInfo":{"address":"325 Broadway, E/NE31","city":"Boulder","constraints":"Please cite original publication, online resource, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, title, online resource, and date accessed. The appearance of external links associated with a dataset does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site.","country":"USA","dataCenterUrl":"https://www.ncdc.noaa.gov/data-access/paleoclimatology-data","email":"paleo@noaa.gov","fax":"303-497-6513","longName":"National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce ","phone":"303-497-6280","postalCode":"80305-3328","shortName":"DOC/NOAA/NESDIS/NCEI","state":"CO","type":"CONTACT INFORMATION"},"contributionDate":"2011-10-16","dataPublisher":"NOAA","dataType":"ICE CORES","dataTypeInformation":"https://www.ncdc.noaa.gov/data-access/paleoclimatology-data/datasets/ice-core","difMetadataLink":"http://www1.ncdc.noaa.gov/pub/data/metadata/published/paleo/dif/xml/noaa-icecore-12256.xml","doi":null,"earliestYearBP":0,"earliestYearCE":1950,"entryId":"noaa-icecore-12256","funding":[{"fundingAgency":"US National Science Foundation","fundingGrant":"OPP0806450"}],"investigators":"Petrenko, V.V.; Severinghaus, J.","mostRecentYearBP":-55,"mostRecentYearCE":2005,"onlineResourceLink":"https://www.ncdc.noaa.gov/paleo/study/12256","originalSource":null,"publication":[{"abstract":"The cause of a large increase of atmospheric methane concentration \r\nduring the Younger Dryas-Preboreal abrupt climatic transition \r\n(~11,600 years ago) has been the subject of much debate. \r\nThe carbon-14 (14C) content of methane (14CH4) should distinguish \r\nbetween wetland and clathrate contributions to this increase. \r\nWe present measurements of 14CH4 in glacial ice, targeting this \r\ntransition, performed by using ice samples obtained from an \r\nablation site in west Greenland.  Measured 14CH4 values were \r\nhigher than predicted under any scenario. Sample 14CH4 appears \r\nto be elevated by direct cosmogenic 14C production in ice. \r\n14C of CO was measured to better understand this process \r\nand correct the sample 14CH4. Corrected results suggest that \r\nwetland sources were likely responsible for the majority \r\nof the Younger Dryas–Preboreal CH4 rise.\r\n","author":null,"citation":"Petrenko, V.V., A.M. Smith, E.J. Brook, D. Lowe, K. Riedel, \r\nG. Brailsford, Q. Hua, H. Schaefer, N. Reeh, R.F. Weiss, \r\nD. Etheridge, and J.P. Severinghaus. 2009. \r\n14CH4 Measurements in Greenland Ice: Investigating Last Glacial \r\nTermination CH4 Sources. \r\nScience, Vol. 324, pp. 506-508, 24 April 2009.\r\n10.1126/science.1168909\r\n","edition":null,"identifier":{"id":"10.1126/science.1168909","type":"doi","url":"http://dx.doi.org/10.1126/science.1168909"},"issue":null,"journal":"Science","pages":null,"pubRank":"1","pubYear":2009,"reportNumber":null,"title":"14CH4 Measurements in Greenland Ice: Investigating Last Glacial  Termination CH4 Sources","type":"publication","volume":null}],"reconstruction":"N","scienceKeywords":null,"site":[{"NOAASiteId":"52442","geo":{"geoType":"Feature","geometry":{"coordinates":["72.57963","-38.49253"],"type":"POINT"},"properties":{"easternmostLongitude":"-38.49253","maxElevationMeters":"3200","minElevationMeters":"3200","northernmostLatitude":"72.57963","southernmostLatitude":"72.57963","westernmostLongitude":"-38.49253"}},"locationName":"Continent>North America>Greenland","mappable":"Y","paleoData":[{"NOAADataTableId":"20597","coreLengthMeters":6,"dataFile":[{"NOAAKeywords":["earth science>paleoclimate>ice core>radiogenic isotopes"],"fileUrl":"https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/summitfirn14ch4.txt","linkText":"summitfirn14ch4.txt","urlDescription":"Data","variables":[{"cvAdditionalInfo":null,"cvDataType":"ICE CORES","cvDetail":null,"cvError":null,"cvFormat":"Numeric","cvMaterial":null,"cvMethod":null,"cvSeasonality":null,"cvShortName":null,"cvUnit":"unspecified unit","cvWhat":"depth variable>depth>depth at sample end"},{"cvAdditionalInfo":null,"cvDataType":"ICE CORES","cvDetail":null,"cvError":null,"cvFormat":"Numeric","cvMaterial":null,"cvMethod":null,"cvSeasonality":null,"cvShortName":null,"cvUnit":"unspecified unit","cvWhat":"depth variable>depth>depth at sample start"},{"cvAdditionalInfo":null,"cvDataType":"ICE CORES","cvDetail":null,"cvError":null,"cvFormat":"Numeric","cvMaterial":"chemical composition>compound>organic compound>hydrocarbon>alkane>n-alkane>methane","cvMethod":"accelerator mass spectrometry","cvSeasonality":null,"cvShortName":null,"cvUnit":"molecule per gram","cvWhat":"chemical composition>isotope>single isotope concentration>14C"},{"cvAdditionalInfo":null,"cvDataType":"ICE CORES","cvDetail":null,"cvError":null,"cvFormat":"Numeric","cvMaterial":"chemical composition>compound>inorganic compound>carbon monoxide","cvMethod":"accelerator mass spectrometry","cvSeasonality":null,"cvShortName":null,"cvUnit":"molecule per gram","cvWhat":"chemical composition>isotope>single isotope concentration>14C"},{"cvAdditionalInfo":"modeled","cvDataType":"ICE CORES","cvDetail":null,"cvError":null,"cvFormat":"Numeric","cvMaterial":"chemical composition>compound>inorganic compound>carbon monoxide","cvMethod":"accelerator mass spectrometry","cvSeasonality":null,"cvShortName":null,"cvUnit":"molecule per gram","cvWhat":"chemical composition>isotope>single isotope concentration>14C"}]},{"NOAAKeywords":["earth science>paleoclimate>ice core>radiogenic isotopes"],"fileUrl":"https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/summitfirn14ch4.xls","linkText":"summitfirn14ch4.xls","urlDescription":"Data","variables":[]}],"dataTableName":"SummitFirn","dataTableNotes":null,"earliestYear":1950,"earliestYearBP":0,"earliestYearCE":1950,"mostRecentYear":2005,"mostRecentYearBP":-55,"mostRecentYearCE":2005,"species":[],"timeUnit":"AD"}],"siteName":"Summit Firn"}],"studyCode":null,"studyName":"Summit, Greenland Firn Cosmogenic 14CH4 Data ","studyNotes":"This project successfully examined the question of whether or not \ncosmic ray-produced 14C forms radiomethane (14CH4) in polar firn. \nFirn samples from ~4.5 m depth were taken at Summit, Greenland. \nAround 1000 kg of firn per sample was melted in the presence of \na 14C-free carrier gas to extract gases from the firn matrix. \nThe findings indicate a small but clearly present cosmogenic \n14CH4 component. A larger cosmogenic 14C – carbon monoxide\n(14CO) component was also found. The results further indicated \nthat almost all cosmogenic 14C is being lost rapidly from the \nfirn matrix at this depth level. These results confirm a \nsurprising earlier finding (Petrenko et al., 2009) that \ncosmogenic 14CH4 may be present in glacial ice. Work using \npaleoatmospheric 14CH4 to study the fossil source contribution \nto the methane budget therefore needs to take the cosmogenic \ncomponent into account. The results are currently \nin preparation for publication. \n\nThe firn samples were collected between Jul 29 and Aug 18, 2009.\n\nINSTRUMENT AND METHOD DESCRIPTION\nThe field and analytical system for determinations of in-situ \ncosmogenic 14CO and 14CH4 in glacial ice and firn have been \ndescribed in (Petrenko et al., 2008a; Petrenko et al., 2008b; \nPetrenko et al., 2009). This system involves the melt-extraction \nof occluded air from very large volumes of glacial ice or at \nthe sampling / ice coring site. Briefly, the present field system \nconsists of a large chemically polished aluminum vacuum melting \ntank (~670 L internal volume) and a series vacuum and transfer \npumps. The ice is loaded into the tank, and the headspace is \nevacuated and flushed 3x with either ultra-high purity (UHP) air, \nnitrogen or argon. The ice is then melted, releasing the ancient \nair into the headspace. This air is then recirculated through \nthe tank via a bubbler manifold at the bottom, equilibrating \nall the gases between the water and the headspace. The air \nis then extracted from the tank by clean diaphragm transfer \npumps and stored in electropolished stainless steel canisters \nfor further laboratory handling and analyses. In the laboratory, \nthe air is first processed through a system that converts either \nCH4 or CO to CO2, and captures this CO2 for further handling. \nIn the case of CH4 processing, H2O, CO2, N2O and other \ncondensibles are first removed by a series of traps at liquid \nnitrogen temperature. CO is then quantitatively oxidized to CO2 \nby the Sofonocat reagent and subsequently removed by further \ncryotraps. CH4 is then combusted to CO2 by passing the air \nthrough a 800°C furnace containing platinized quartz wool. \nThe CH4-derived CO2 is then captured. This CO2 is then converted \nto graphite over ultra-high-purity iron powder and subsequently \nmeasured for 14C by AMS. The combined procedural 14CH4 blank \nfor all steps of sampling handling was determined to be \n0.75 ± 0.38 pMC, on the basis of 72 processed blank \nand standard samples (Petrenko et al., 2008b). For CO analyses, \nthe sample handling is very similar except that the air bypasses \nSofnocat, and the furnace temperature is reduced from 800 to 150 °C. \nThis allows for complete combustion of CO while CH4 passes \nthrough unaffected.\n\nDATA COLLECTION AND PROCESSING\nThe 14CH4 data are corrected for ambient air added to the samples \nfrom air bubbles in the firn as well as for the procedural blank. \nFor 14CO, the ambient air correction is insignificant, but the \nsamples are corrected for the procedural blank.\n\n","version":"1.0","xmlId":"10318"}