Pore morphology of polar firn around closure revealed by X-ray tomography
Understanding the slow densification process of polar firn into ice is essential in order to constrain the age difference between the ice matrix and entrapped gases. The progressive microstructure evolution of the firn column with depth leads to pore closure and gas entrapment. Air transport models...
Published in: | The Cryosphere |
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Copernicus Publications
2018
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Online Access: | https://doi.org/10.5194/tc-12-2481-2018 https://www.the-cryosphere.net/12/2481/2018/tc-12-2481-2018.pdf https://doaj.org/article/85eea5a0c05c4e0ca478e6468a6cbdf1 |
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fttriple:oai:gotriple.eu:oai:doaj.org/article:85eea5a0c05c4e0ca478e6468a6cbdf1 2023-05-15T13:59:11+02:00 Pore morphology of polar firn around closure revealed by X-ray tomography A. Burr C. Ballot P. Lhuissier P. Martinerie C. L. Martin A. Philip 2018-07-01 https://doi.org/10.5194/tc-12-2481-2018 https://www.the-cryosphere.net/12/2481/2018/tc-12-2481-2018.pdf https://doaj.org/article/85eea5a0c05c4e0ca478e6468a6cbdf1 en eng Copernicus Publications doi:10.5194/tc-12-2481-2018 1994-0416 1994-0424 https://www.the-cryosphere.net/12/2481/2018/tc-12-2481-2018.pdf https://doaj.org/article/85eea5a0c05c4e0ca478e6468a6cbdf1 undefined The Cryosphere, Vol 12, Pp 2481-2500 (2018) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2018 fttriple https://doi.org/10.5194/tc-12-2481-2018 2023-01-22T19:26:04Z Understanding the slow densification process of polar firn into ice is essential in order to constrain the age difference between the ice matrix and entrapped gases. The progressive microstructure evolution of the firn column with depth leads to pore closure and gas entrapment. Air transport models in the firn usually include a closed porosity profile based on available data. Pycnometry or melting–refreezing techniques have been used to obtain the ratio of closed to total porosity and air content in closed pores, respectively. X-ray-computed tomography is complementary to these methods, as it enables one to obtain the full pore network in 3-D. This study takes advantage of this nondestructive technique to discuss the morphological evolution of pores on four different Antarctic sites. The computation of refined geometrical parameters for the very cold polar sites Dome C and Lock In (the two Antarctic plateau sites studied here) provides new information that could be used in further studies. The comparison of these two sites shows a more tortuous pore network at Lock In than at Dome C, which should result in older gas ages in deep firn at Lock In. A comprehensive estimation of the different errors related to X-ray tomography and to the sample variability has been performed. The procedure described here may be used as a guideline for further experimental characterization of firn samples. We show that the closed-to-total porosity ratio, which is classically used for the detection of pore closure, is strongly affected by the sample size, the image reconstruction, and spatial heterogeneities. In this work, we introduce an alternative parameter, the connectivity index, which is practically independent of sample size and image acquisition conditions, and that accurately predicts the close-off depth and density. Its strength also lies in its simple computation, without any assumption of the pore status (open or close). The close-off prediction is obtained for Dome C and Lock In, without any further numerical simulations ... Article in Journal/Newspaper Antarc* Antarctic The Cryosphere Unknown Antarctic The Cryosphere 12 7 2481 2500 |
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Open Polar |
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language |
English |
topic |
geo envir |
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geo envir A. Burr C. Ballot P. Lhuissier P. Martinerie C. L. Martin A. Philip Pore morphology of polar firn around closure revealed by X-ray tomography |
topic_facet |
geo envir |
description |
Understanding the slow densification process of polar firn into ice is essential in order to constrain the age difference between the ice matrix and entrapped gases. The progressive microstructure evolution of the firn column with depth leads to pore closure and gas entrapment. Air transport models in the firn usually include a closed porosity profile based on available data. Pycnometry or melting–refreezing techniques have been used to obtain the ratio of closed to total porosity and air content in closed pores, respectively. X-ray-computed tomography is complementary to these methods, as it enables one to obtain the full pore network in 3-D. This study takes advantage of this nondestructive technique to discuss the morphological evolution of pores on four different Antarctic sites. The computation of refined geometrical parameters for the very cold polar sites Dome C and Lock In (the two Antarctic plateau sites studied here) provides new information that could be used in further studies. The comparison of these two sites shows a more tortuous pore network at Lock In than at Dome C, which should result in older gas ages in deep firn at Lock In. A comprehensive estimation of the different errors related to X-ray tomography and to the sample variability has been performed. The procedure described here may be used as a guideline for further experimental characterization of firn samples. We show that the closed-to-total porosity ratio, which is classically used for the detection of pore closure, is strongly affected by the sample size, the image reconstruction, and spatial heterogeneities. In this work, we introduce an alternative parameter, the connectivity index, which is practically independent of sample size and image acquisition conditions, and that accurately predicts the close-off depth and density. Its strength also lies in its simple computation, without any assumption of the pore status (open or close). The close-off prediction is obtained for Dome C and Lock In, without any further numerical simulations ... |
format |
Article in Journal/Newspaper |
author |
A. Burr C. Ballot P. Lhuissier P. Martinerie C. L. Martin A. Philip |
author_facet |
A. Burr C. Ballot P. Lhuissier P. Martinerie C. L. Martin A. Philip |
author_sort |
A. Burr |
title |
Pore morphology of polar firn around closure revealed by X-ray tomography |
title_short |
Pore morphology of polar firn around closure revealed by X-ray tomography |
title_full |
Pore morphology of polar firn around closure revealed by X-ray tomography |
title_fullStr |
Pore morphology of polar firn around closure revealed by X-ray tomography |
title_full_unstemmed |
Pore morphology of polar firn around closure revealed by X-ray tomography |
title_sort |
pore morphology of polar firn around closure revealed by x-ray tomography |
publisher |
Copernicus Publications |
publishDate |
2018 |
url |
https://doi.org/10.5194/tc-12-2481-2018 https://www.the-cryosphere.net/12/2481/2018/tc-12-2481-2018.pdf https://doaj.org/article/85eea5a0c05c4e0ca478e6468a6cbdf1 |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic The Cryosphere |
genre_facet |
Antarc* Antarctic The Cryosphere |
op_source |
The Cryosphere, Vol 12, Pp 2481-2500 (2018) |
op_relation |
doi:10.5194/tc-12-2481-2018 1994-0416 1994-0424 https://www.the-cryosphere.net/12/2481/2018/tc-12-2481-2018.pdf https://doaj.org/article/85eea5a0c05c4e0ca478e6468a6cbdf1 |
op_rights |
undefined |
op_doi |
https://doi.org/10.5194/tc-12-2481-2018 |
container_title |
The Cryosphere |
container_volume |
12 |
container_issue |
7 |
container_start_page |
2481 |
op_container_end_page |
2500 |
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