Observations of the creep of polar firn
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 (micr...
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Cambridge University Press
2022
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ftdoajarticles:oai:doaj.org/article:63d685e65dfd4751a1e611e08ea0129b 2023-05-15T16:29:41+02:00 Observations of the creep of polar firn Yuan Li Ian Baker 2022-04-01T00:00:00Z https://doi.org/10.1017/jog.2021.91 https://doaj.org/article/63d685e65dfd4751a1e611e08ea0129b EN eng Cambridge University Press https://www.cambridge.org/core/product/identifier/S0022143021000915/type/journal_article https://doaj.org/toc/0022-1430 https://doaj.org/toc/1727-5652 doi:10.1017/jog.2021.91 0022-1430 1727-5652 https://doaj.org/article/63d685e65dfd4751a1e611e08ea0129b Journal of Glaciology, Vol 68, Pp 269-287 (2022) Creep firn ice microstructural evolution stress exponent Environmental sciences GE1-350 Meteorology. Climatology QC851-999 article 2022 ftdoajarticles https://doi.org/10.1017/jog.2021.91 2023-03-12T01:30:54Z 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 Directory of Open Access Journals: DOAJ Articles Greenland Journal of Glaciology 68 268 269 287 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Creep firn ice microstructural evolution stress exponent Environmental sciences GE1-350 Meteorology. Climatology QC851-999 |
spellingShingle |
Creep firn ice microstructural evolution stress exponent Environmental sciences GE1-350 Meteorology. Climatology QC851-999 Yuan Li Ian Baker Observations of the creep of polar firn |
topic_facet |
Creep firn ice microstructural evolution stress exponent Environmental sciences GE1-350 Meteorology. Climatology QC851-999 |
description |
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. |
format |
Article in Journal/Newspaper |
author |
Yuan Li Ian Baker |
author_facet |
Yuan Li Ian Baker |
author_sort |
Yuan Li |
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 |
publishDate |
2022 |
url |
https://doi.org/10.1017/jog.2021.91 https://doaj.org/article/63d685e65dfd4751a1e611e08ea0129b |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Journal of Glaciology |
genre_facet |
Greenland Journal of Glaciology |
op_source |
Journal of Glaciology, Vol 68, Pp 269-287 (2022) |
op_relation |
https://www.cambridge.org/core/product/identifier/S0022143021000915/type/journal_article https://doaj.org/toc/0022-1430 https://doaj.org/toc/1727-5652 doi:10.1017/jog.2021.91 0022-1430 1727-5652 https://doaj.org/article/63d685e65dfd4751a1e611e08ea0129b |
op_doi |
https://doi.org/10.1017/jog.2021.91 |
container_title |
Journal of Glaciology |
container_volume |
68 |
container_issue |
268 |
container_start_page |
269 |
op_container_end_page |
287 |
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1766019387982086144 |