Observations of the creep of polar firn
Abstract Constant-load creep tests were performed at −10°C at various compressive stresses from 0.05 to 0.75 MPa on specimens taken every 10 m along a firn core extracted at Summit, Greenland in June 2017. The microstructures before and after creep testing were examined using both X-ray microtomogra...
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Cambridge University Press (CUP)
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Online Access: | http://dx.doi.org/10.1017/jog.2021.91 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143021000915 |
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crcambridgeupr:10.1017/jog.2021.91 2024-06-23T07:53:21+00:00 Observations of the creep of polar firn Li, Yuan Baker, Ian National Science Foundation Arctic Natural Science 2021 http://dx.doi.org/10.1017/jog.2021.91 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143021000915 en eng Cambridge University Press (CUP) http://creativecommons.org/licenses/by/4.0/ Journal of Glaciology volume 68, issue 268, page 269-287 ISSN 0022-1430 1727-5652 journal-article 2021 crcambridgeupr https://doi.org/10.1017/jog.2021.91 2024-05-29T08:09:49Z Abstract Constant-load creep tests were performed at −10°C at various compressive stresses from 0.05 to 0.75 MPa on specimens taken every 10 m along a firn core extracted at Summit, Greenland in June 2017. The microstructures before and after creep testing were examined using both X-ray microtomography (micro-CT) and optical images from thin sections. An Andrade-like equation was used to describe the primary creep behavior and yielded the time exponent k of 0.17–0.76. The onset of secondary creep occurred at strains of ~0.5–3% but was sometimes not observed at all in shallow firn specimens and at stresses ⩽0.43 MPa even for strain up to 32%. For the 50–80 m firn crept at stresses ⩾0.55 MPa, secondary creep occurred at strains of 2.6 ± 0.28%, and the stress exponent, n , in Glen's law, was found to range from 4.1 to 4.6, similar to those observed for fully dense ice. Micro-CT observations of crept specimens showed that in most cases, the specific surface area, the total porosity and the structure model index decreased, while the structure thickness increased with increasing density. These microstructural characteristics are consistent with the densification of the firn. Optical images from thin sections showed that recrystallization occurred in some specimens that had undergone secondary creep. Article in Journal/Newspaper Greenland Journal of Glaciology Cambridge University Press Greenland Journal of Glaciology 1 19 |
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Open Polar |
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Cambridge University Press |
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crcambridgeupr |
language |
English |
description |
Abstract Constant-load creep tests were performed at −10°C at various compressive stresses from 0.05 to 0.75 MPa on specimens taken every 10 m along a firn core extracted at Summit, Greenland in June 2017. The microstructures before and after creep testing were examined using both X-ray microtomography (micro-CT) and optical images from thin sections. An Andrade-like equation was used to describe the primary creep behavior and yielded the time exponent k of 0.17–0.76. The onset of secondary creep occurred at strains of ~0.5–3% but was sometimes not observed at all in shallow firn specimens and at stresses ⩽0.43 MPa even for strain up to 32%. For the 50–80 m firn crept at stresses ⩾0.55 MPa, secondary creep occurred at strains of 2.6 ± 0.28%, and the stress exponent, n , in Glen's law, was found to range from 4.1 to 4.6, similar to those observed for fully dense ice. Micro-CT observations of crept specimens showed that in most cases, the specific surface area, the total porosity and the structure model index decreased, while the structure thickness increased with increasing density. These microstructural characteristics are consistent with the densification of the firn. Optical images from thin sections showed that recrystallization occurred in some specimens that had undergone secondary creep. |
author2 |
National Science Foundation Arctic Natural Science |
format |
Article in Journal/Newspaper |
author |
Li, Yuan Baker, Ian |
spellingShingle |
Li, Yuan Baker, Ian Observations of the creep of polar firn |
author_facet |
Li, Yuan Baker, Ian |
author_sort |
Li, Yuan |
title |
Observations of the creep of polar firn |
title_short |
Observations of the creep of polar firn |
title_full |
Observations of the creep of polar firn |
title_fullStr |
Observations of the creep of polar firn |
title_full_unstemmed |
Observations of the creep of polar firn |
title_sort |
observations of the creep of polar firn |
publisher |
Cambridge University Press (CUP) |
publishDate |
2021 |
url |
http://dx.doi.org/10.1017/jog.2021.91 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143021000915 |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Journal of Glaciology |
genre_facet |
Greenland Journal of Glaciology |
op_source |
Journal of Glaciology volume 68, issue 268, page 269-287 ISSN 0022-1430 1727-5652 |
op_rights |
http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.1017/jog.2021.91 |
container_title |
Journal of Glaciology |
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1 |
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19 |
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1802644959037227008 |