Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland
Air was sampled from the porous firn layer at the NEEM site in Northern Greenland. We use an ensemble of ten reference tracers of known atmospheric history to characterise the transport properties of the site. By analysing uncertainties in both data and the reference gas atmospheric histories, we ca...
Published in: | Atmospheric Chemistry and Physics |
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2012
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Online Access: | https://doi.org/10.5194/acp-12-4259-2012 https://doaj.org/article/6f7431feb1bc4c1e80ba7746c1688aae |
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ftdoajarticles:oai:doaj.org/article:6f7431feb1bc4c1e80ba7746c1688aae 2023-05-15T16:28:30+02:00 Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland C. Buizert P. Martinerie V. V. Petrenko J. P. Severinghaus C. M. Trudinger E. Witrant J. L. Rosen A. J. Orsi M. Rubino D. M. Etheridge L. P. Steele C. Hogan J. C. Laube W. T. Sturges V. A. Levchenko A. M. Smith I. Levin T. J. Conway E. J. Dlugokencky P. M. Lang K. Kawamura T. M. Jenk J. W. C. White T. Sowers J. Schwander T. Blunier 2012-05-01T00:00:00Z https://doi.org/10.5194/acp-12-4259-2012 https://doaj.org/article/6f7431feb1bc4c1e80ba7746c1688aae EN eng Copernicus Publications http://www.atmos-chem-phys.net/12/4259/2012/acp-12-4259-2012.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 doi:10.5194/acp-12-4259-2012 1680-7316 1680-7324 https://doaj.org/article/6f7431feb1bc4c1e80ba7746c1688aae Atmospheric Chemistry and Physics, Vol 12, Iss 9, Pp 4259-4277 (2012) Physics QC1-999 Chemistry QD1-999 article 2012 ftdoajarticles https://doi.org/10.5194/acp-12-4259-2012 2022-12-31T13:58:16Z Air was sampled from the porous firn layer at the NEEM site in Northern Greenland. We use an ensemble of ten reference tracers of known atmospheric history to characterise the transport properties of the site. By analysing uncertainties in both data and the reference gas atmospheric histories, we can objectively assign weights to each of the gases used for the depth-diffusivity reconstruction. We define an objective root mean square criterion that is minimised in the model tuning procedure. Each tracer constrains the firn profile differently through its unique atmospheric history and free air diffusivity, making our multiple-tracer characterisation method a clear improvement over the commonly used single-tracer tuning. Six firn air transport models are tuned to the NEEM site; all models successfully reproduce the data within a 1σ Gaussian distribution. A comparison between two replicate boreholes drilled 64 m apart shows differences in measured mixing ratio profiles that exceed the experimental error. We find evidence that diffusivity does not vanish completely in the lock-in zone, as is commonly assumed. The ice age- gas age difference (Δage) at the firn-ice transition is calculated to be 182 +3 −9 yr. We further present the first intercomparison study of firn air models, where we introduce diagnostic scenarios designed to probe specific aspects of the model physics. Our results show that there are major differences in the way the models handle advective transport. Furthermore, diffusive fractionation of isotopes in the firn is poorly constrained by the models, which has consequences for attempts to reconstruct the isotopic composition of trace gases back in time using firn air and ice core records. Article in Journal/Newspaper Greenland ice core Directory of Open Access Journals: DOAJ Articles Greenland Atmospheric Chemistry and Physics 12 9 4259 4277 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Physics QC1-999 Chemistry QD1-999 |
spellingShingle |
Physics QC1-999 Chemistry QD1-999 C. Buizert P. Martinerie V. V. Petrenko J. P. Severinghaus C. M. Trudinger E. Witrant J. L. Rosen A. J. Orsi M. Rubino D. M. Etheridge L. P. Steele C. Hogan J. C. Laube W. T. Sturges V. A. Levchenko A. M. Smith I. Levin T. J. Conway E. J. Dlugokencky P. M. Lang K. Kawamura T. M. Jenk J. W. C. White T. Sowers J. Schwander T. Blunier Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland |
topic_facet |
Physics QC1-999 Chemistry QD1-999 |
description |
Air was sampled from the porous firn layer at the NEEM site in Northern Greenland. We use an ensemble of ten reference tracers of known atmospheric history to characterise the transport properties of the site. By analysing uncertainties in both data and the reference gas atmospheric histories, we can objectively assign weights to each of the gases used for the depth-diffusivity reconstruction. We define an objective root mean square criterion that is minimised in the model tuning procedure. Each tracer constrains the firn profile differently through its unique atmospheric history and free air diffusivity, making our multiple-tracer characterisation method a clear improvement over the commonly used single-tracer tuning. Six firn air transport models are tuned to the NEEM site; all models successfully reproduce the data within a 1σ Gaussian distribution. A comparison between two replicate boreholes drilled 64 m apart shows differences in measured mixing ratio profiles that exceed the experimental error. We find evidence that diffusivity does not vanish completely in the lock-in zone, as is commonly assumed. The ice age- gas age difference (Δage) at the firn-ice transition is calculated to be 182 +3 −9 yr. We further present the first intercomparison study of firn air models, where we introduce diagnostic scenarios designed to probe specific aspects of the model physics. Our results show that there are major differences in the way the models handle advective transport. Furthermore, diffusive fractionation of isotopes in the firn is poorly constrained by the models, which has consequences for attempts to reconstruct the isotopic composition of trace gases back in time using firn air and ice core records. |
format |
Article in Journal/Newspaper |
author |
C. Buizert P. Martinerie V. V. Petrenko J. P. Severinghaus C. M. Trudinger E. Witrant J. L. Rosen A. J. Orsi M. Rubino D. M. Etheridge L. P. Steele C. Hogan J. C. Laube W. T. Sturges V. A. Levchenko A. M. Smith I. Levin T. J. Conway E. J. Dlugokencky P. M. Lang K. Kawamura T. M. Jenk J. W. C. White T. Sowers J. Schwander T. Blunier |
author_facet |
C. Buizert P. Martinerie V. V. Petrenko J. P. Severinghaus C. M. Trudinger E. Witrant J. L. Rosen A. J. Orsi M. Rubino D. M. Etheridge L. P. Steele C. Hogan J. C. Laube W. T. Sturges V. A. Levchenko A. M. Smith I. Levin T. J. Conway E. J. Dlugokencky P. M. Lang K. Kawamura T. M. Jenk J. W. C. White T. Sowers J. Schwander T. Blunier |
author_sort |
C. Buizert |
title |
Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland |
title_short |
Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland |
title_full |
Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland |
title_fullStr |
Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland |
title_full_unstemmed |
Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland |
title_sort |
gas transport in firn: multiple-tracer characterisation and model intercomparison for neem, northern greenland |
publisher |
Copernicus Publications |
publishDate |
2012 |
url |
https://doi.org/10.5194/acp-12-4259-2012 https://doaj.org/article/6f7431feb1bc4c1e80ba7746c1688aae |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland ice core |
genre_facet |
Greenland ice core |
op_source |
Atmospheric Chemistry and Physics, Vol 12, Iss 9, Pp 4259-4277 (2012) |
op_relation |
http://www.atmos-chem-phys.net/12/4259/2012/acp-12-4259-2012.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 doi:10.5194/acp-12-4259-2012 1680-7316 1680-7324 https://doaj.org/article/6f7431feb1bc4c1e80ba7746c1688aae |
op_doi |
https://doi.org/10.5194/acp-12-4259-2012 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
12 |
container_issue |
9 |
container_start_page |
4259 |
op_container_end_page |
4277 |
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1766018149012996096 |