Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps
Crystal orientation fabric (COF) analysis provides information about the c -axis orientation of ice grains and the associated anisotropy and microstructural information about deformation and recrystallisation processes within the glacier. This information can be used to introduce modules that fully...
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ftcopernicus:oai:publications.copernicus.org:tc85547 2023-05-15T16:39:21+02:00 Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps Hellmann, Sebastian Kerch, Johanna Weikusat, Ilka Bauder, Andreas Grab, Melchior Jouvet, Guillaume Schwikowski, Margit Maurer, Hansruedi 2021-02-12 application/pdf https://doi.org/10.5194/tc-15-677-2021 https://tc.copernicus.org/articles/15/677/2021/ eng eng doi:10.5194/tc-15-677-2021 https://tc.copernicus.org/articles/15/677/2021/ eISSN: 1994-0424 Text 2021 ftcopernicus https://doi.org/10.5194/tc-15-677-2021 2021-02-15T17:22:13Z Crystal orientation fabric (COF) analysis provides information about the c -axis orientation of ice grains and the associated anisotropy and microstructural information about deformation and recrystallisation processes within the glacier. This information can be used to introduce modules that fully describe the microstructural anisotropy or at least direction-dependent enhancement factors for glacier modelling. The COF was studied at an ice core that was obtained from the temperate Rhonegletscher, located in the central Swiss Alps. Seven samples, extracted at depths between 2 and 79 m, were analysed with an automatic fabric analyser. The COF analysis revealed conspicuous four-maxima patterns of the c -axis orientations at all depths. Additional data, such as microstructural images, produced during the ice sample preparation process, were considered to interpret these patterns. Furthermore, repeated high-precision global navigation satellite system (GNSS) surveying allowed the local glacier flow direction to be determined. The relative movements of the individual surveying points indicated longitudinal compressive stresses parallel to the glacier flow. Finally, numerical modelling of the ice flow permitted estimation of the local stress distribution. An integrated analysis of all the data sets provided indications and suggestions for the development of the four-maxima patterns. The centroid of the four-maxima patterns of the individual core samples and the coinciding maximum eigenvector approximately align with the compressive stress directions obtained from numerical modelling with an exception for the deepest sample. The clustering of the c axes in four maxima surrounding the predominant compressive stress direction is most likely the result of a fast migration recrystallisation. This interpretation is supported by air bubble analysis of large-area scanning macroscope (LASM) images. Our results indicate that COF studies, which have so far predominantly been performed on cold ice samples from the polar regions, can also provide valuable insights into the stress and strain rate distribution within temperate glaciers. Text ice core Copernicus Publications: E-Journals The Cryosphere 15 2 677 694 |
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Copernicus Publications: E-Journals |
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ftcopernicus |
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English |
description |
Crystal orientation fabric (COF) analysis provides information about the c -axis orientation of ice grains and the associated anisotropy and microstructural information about deformation and recrystallisation processes within the glacier. This information can be used to introduce modules that fully describe the microstructural anisotropy or at least direction-dependent enhancement factors for glacier modelling. The COF was studied at an ice core that was obtained from the temperate Rhonegletscher, located in the central Swiss Alps. Seven samples, extracted at depths between 2 and 79 m, were analysed with an automatic fabric analyser. The COF analysis revealed conspicuous four-maxima patterns of the c -axis orientations at all depths. Additional data, such as microstructural images, produced during the ice sample preparation process, were considered to interpret these patterns. Furthermore, repeated high-precision global navigation satellite system (GNSS) surveying allowed the local glacier flow direction to be determined. The relative movements of the individual surveying points indicated longitudinal compressive stresses parallel to the glacier flow. Finally, numerical modelling of the ice flow permitted estimation of the local stress distribution. An integrated analysis of all the data sets provided indications and suggestions for the development of the four-maxima patterns. The centroid of the four-maxima patterns of the individual core samples and the coinciding maximum eigenvector approximately align with the compressive stress directions obtained from numerical modelling with an exception for the deepest sample. The clustering of the c axes in four maxima surrounding the predominant compressive stress direction is most likely the result of a fast migration recrystallisation. This interpretation is supported by air bubble analysis of large-area scanning macroscope (LASM) images. Our results indicate that COF studies, which have so far predominantly been performed on cold ice samples from the polar regions, can also provide valuable insights into the stress and strain rate distribution within temperate glaciers. |
format |
Text |
author |
Hellmann, Sebastian Kerch, Johanna Weikusat, Ilka Bauder, Andreas Grab, Melchior Jouvet, Guillaume Schwikowski, Margit Maurer, Hansruedi |
spellingShingle |
Hellmann, Sebastian Kerch, Johanna Weikusat, Ilka Bauder, Andreas Grab, Melchior Jouvet, Guillaume Schwikowski, Margit Maurer, Hansruedi Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps |
author_facet |
Hellmann, Sebastian Kerch, Johanna Weikusat, Ilka Bauder, Andreas Grab, Melchior Jouvet, Guillaume Schwikowski, Margit Maurer, Hansruedi |
author_sort |
Hellmann, Sebastian |
title |
Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps |
title_short |
Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps |
title_full |
Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps |
title_fullStr |
Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps |
title_full_unstemmed |
Crystallographic analysis of temperate ice on Rhonegletscher, Swiss Alps |
title_sort |
crystallographic analysis of temperate ice on rhonegletscher, swiss alps |
publishDate |
2021 |
url |
https://doi.org/10.5194/tc-15-677-2021 https://tc.copernicus.org/articles/15/677/2021/ |
genre |
ice core |
genre_facet |
ice core |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-15-677-2021 https://tc.copernicus.org/articles/15/677/2021/ |
op_doi |
https://doi.org/10.5194/tc-15-677-2021 |
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