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...
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Online Access: | https://doi.org/10.5194/acp-12-4259-2012 https://www.atmos-chem-phys.net/12/4259/2012/ |
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ftcopernicus:oai:publications.copernicus.org:acp11388 2023-05-15T16:28:29+02:00 Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland Buizert, C. Martinerie, P. Petrenko, V. V. Severinghaus, J. P. Trudinger, C. M. Witrant, E. Rosen, J. L. Orsi, A. J. Rubino, M. Etheridge, D. M. Steele, L. P. Hogan, C. Laube, J. C. Sturges, W. T. Levchenko, V. A. Smith, A. M. Levin, I. Conway, T. J. Dlugokencky, E. J. Lang, P. M. Kawamura, K. Jenk, T. M. White, J. W. C. Sowers, T. Schwander, J. Blunier, T. 2018-01-15 application/pdf https://doi.org/10.5194/acp-12-4259-2012 https://www.atmos-chem-phys.net/12/4259/2012/ eng eng doi:10.5194/acp-12-4259-2012 https://www.atmos-chem-phys.net/12/4259/2012/ eISSN: 1680-7324 Text 2018 ftcopernicus https://doi.org/10.5194/acp-12-4259-2012 2019-12-24T09:56:17Z 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. Text Greenland ice core Copernicus Publications: E-Journals Greenland Atmospheric Chemistry and Physics 12 9 4259 4277 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
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 |
Text |
author |
Buizert, C. Martinerie, P. Petrenko, V. V. Severinghaus, J. P. Trudinger, C. M. Witrant, E. Rosen, J. L. Orsi, A. J. Rubino, M. Etheridge, D. M. Steele, L. P. Hogan, C. Laube, J. C. Sturges, W. T. Levchenko, V. A. Smith, A. M. Levin, I. Conway, T. J. Dlugokencky, E. J. Lang, P. M. Kawamura, K. Jenk, T. M. White, J. W. C. Sowers, T. Schwander, J. Blunier, T. |
spellingShingle |
Buizert, C. Martinerie, P. Petrenko, V. V. Severinghaus, J. P. Trudinger, C. M. Witrant, E. Rosen, J. L. Orsi, A. J. Rubino, M. Etheridge, D. M. Steele, L. P. Hogan, C. Laube, J. C. Sturges, W. T. Levchenko, V. A. Smith, A. M. Levin, I. Conway, T. J. Dlugokencky, E. J. Lang, P. M. Kawamura, K. Jenk, T. M. White, J. W. C. Sowers, T. Schwander, J. Blunier, T. Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland |
author_facet |
Buizert, C. Martinerie, P. Petrenko, V. V. Severinghaus, J. P. Trudinger, C. M. Witrant, E. Rosen, J. L. Orsi, A. J. Rubino, M. Etheridge, D. M. Steele, L. P. Hogan, C. Laube, J. C. Sturges, W. T. Levchenko, V. A. Smith, A. M. Levin, I. Conway, T. J. Dlugokencky, E. J. Lang, P. M. Kawamura, K. Jenk, T. M. White, J. W. C. Sowers, T. Schwander, J. Blunier, T. |
author_sort |
Buizert, C. |
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 |
publishDate |
2018 |
url |
https://doi.org/10.5194/acp-12-4259-2012 https://www.atmos-chem-phys.net/12/4259/2012/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland ice core |
genre_facet |
Greenland ice core |
op_source |
eISSN: 1680-7324 |
op_relation |
doi:10.5194/acp-12-4259-2012 https://www.atmos-chem-phys.net/12/4259/2012/ |
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 |
_version_ |
1766018131240681472 |