Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records
During rapid variations of the atmospheric mixing ratio of a trace gas, diffusive transport in the porous firn layer atop ice sheets and glaciers alters the isotopic composition of that gas relative to the overlying atmosphere. Records of past atmospheric trace gas isotopic composition from ice core...
Published in: | Earth and Planetary Science Letters |
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Language: | English |
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Online Access: | https://curis.ku.dk/portal/da/publications/assessment-of-diffusive-isotopic-fractionation-in-polar-firn-and-application-to-ice-core-trace-gas-records(1499b016-8566-4797-b8e1-f17f90c171ba).html https://doi.org/10.1016/j.epsl.2012.11.039 http://www.scopus.com/inward/record.url?scp=84871390553&partnerID=8YFLogxK |
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ftcopenhagenunip:oai:pure.atira.dk:publications/1499b016-8566-4797-b8e1-f17f90c171ba 2024-05-12T08:05:11+00:00 Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records Buizert, C. Sowers, T. Blunier, T. 2013-01-01 https://curis.ku.dk/portal/da/publications/assessment-of-diffusive-isotopic-fractionation-in-polar-firn-and-application-to-ice-core-trace-gas-records(1499b016-8566-4797-b8e1-f17f90c171ba).html https://doi.org/10.1016/j.epsl.2012.11.039 http://www.scopus.com/inward/record.url?scp=84871390553&partnerID=8YFLogxK eng eng info:eu-repo/semantics/restrictedAccess Buizert , C , Sowers , T & Blunier , T 2013 , ' Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records ' , Earth and Planetary Science Letters , vol. 361 , pp. 110-119 . https://doi.org/10.1016/j.epsl.2012.11.039 article 2013 ftcopenhagenunip https://doi.org/10.1016/j.epsl.2012.11.039 2024-04-18T00:28:12Z During rapid variations of the atmospheric mixing ratio of a trace gas, diffusive transport in the porous firn layer atop ice sheets and glaciers alters the isotopic composition of that gas relative to the overlying atmosphere. Records of past atmospheric trace gas isotopic composition from ice cores and firn need to be corrected for this diffusive fractionation artifact. We present a novel, semi-empirical method to accurately estimate the magnitude of the diffusive fractionation in the ice core record. Our method (1) consists of a relatively simple analytical calculation; (2) requires only commonly available ice core data; (3) is not subject to the uncertainties inherent to estimating the accumulation rate, temperature, close-off depth and depth-diffusivity relationship back in time; (4) does not require knowledge of the true atmospheric variations, but uses the smoothed records obtained from ice cores; (5) arguably gives more accurate results than a combined firn densification-firn air transport modeling study would. We apply the method to records of CH, CO and NO mixing ratios, and we find that the correction is particularly important for C - . We apply the correction to C - records over the last glacial termination and the 8.2ka event. In both cases the diffusive signal exceeds the analytical precision of the data, and has a significant impact on the observed isotopic trends. For the 8.2ka event the corrected data show an isotopic enrichment in C - for the duration of the event, consistent with reduced wetland emissions. Article in Journal/Newspaper ice core University of Copenhagen: Research Earth and Planetary Science Letters 361 110 119 |
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Open Polar |
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University of Copenhagen: Research |
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ftcopenhagenunip |
language |
English |
description |
During rapid variations of the atmospheric mixing ratio of a trace gas, diffusive transport in the porous firn layer atop ice sheets and glaciers alters the isotopic composition of that gas relative to the overlying atmosphere. Records of past atmospheric trace gas isotopic composition from ice cores and firn need to be corrected for this diffusive fractionation artifact. We present a novel, semi-empirical method to accurately estimate the magnitude of the diffusive fractionation in the ice core record. Our method (1) consists of a relatively simple analytical calculation; (2) requires only commonly available ice core data; (3) is not subject to the uncertainties inherent to estimating the accumulation rate, temperature, close-off depth and depth-diffusivity relationship back in time; (4) does not require knowledge of the true atmospheric variations, but uses the smoothed records obtained from ice cores; (5) arguably gives more accurate results than a combined firn densification-firn air transport modeling study would. We apply the method to records of CH, CO and NO mixing ratios, and we find that the correction is particularly important for C - . We apply the correction to C - records over the last glacial termination and the 8.2ka event. In both cases the diffusive signal exceeds the analytical precision of the data, and has a significant impact on the observed isotopic trends. For the 8.2ka event the corrected data show an isotopic enrichment in C - for the duration of the event, consistent with reduced wetland emissions. |
format |
Article in Journal/Newspaper |
author |
Buizert, C. Sowers, T. Blunier, T. |
spellingShingle |
Buizert, C. Sowers, T. Blunier, T. Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records |
author_facet |
Buizert, C. Sowers, T. Blunier, T. |
author_sort |
Buizert, C. |
title |
Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records |
title_short |
Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records |
title_full |
Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records |
title_fullStr |
Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records |
title_full_unstemmed |
Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records |
title_sort |
assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records |
publishDate |
2013 |
url |
https://curis.ku.dk/portal/da/publications/assessment-of-diffusive-isotopic-fractionation-in-polar-firn-and-application-to-ice-core-trace-gas-records(1499b016-8566-4797-b8e1-f17f90c171ba).html https://doi.org/10.1016/j.epsl.2012.11.039 http://www.scopus.com/inward/record.url?scp=84871390553&partnerID=8YFLogxK |
genre |
ice core |
genre_facet |
ice core |
op_source |
Buizert , C , Sowers , T & Blunier , T 2013 , ' Assessment of diffusive isotopic fractionation in polar firn, and application to ice core trace gas records ' , Earth and Planetary Science Letters , vol. 361 , pp. 110-119 . https://doi.org/10.1016/j.epsl.2012.11.039 |
op_rights |
info:eu-repo/semantics/restrictedAccess |
op_doi |
https://doi.org/10.1016/j.epsl.2012.11.039 |
container_title |
Earth and Planetary Science Letters |
container_volume |
361 |
container_start_page |
110 |
op_container_end_page |
119 |
_version_ |
1798847445642248192 |