Acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core

Abstract. The crystal orientation fabric (COF) in ice cores provides detailed information, such as grain size and distribution and the orientation of the crystals in relation to the large-scale glacier flow. These data are relevant for a profound understanding of the dynamics and deformation history...

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Published in:The Cryosphere
Main Authors: Hellmann, Sebastian, Grab, Melchior, Kerch, Johanna, Löwe, Henning, Bauder, Andreas, Weikusat, Ilka, Maurer, Hansruedi
Format: Article in Journal/Newspaper
Language:English
Published: 2021
Subjects:
Online Access:https://resolver.sub.uni-goettingen.de/purl?gro-2/89196
https://doi.org/10.5194/tc-15-3507-2021
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spelling ftsubgoettingen:oai:publications.goettingen-research-online.de:2/89196 2023-09-05T13:20:11+02:00 Acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core Hellmann, Sebastian Grab, Melchior Kerch, Johanna Löwe, Henning Bauder, Andreas Weikusat, Ilka Maurer, Hansruedi 2021 https://resolver.sub.uni-goettingen.de/purl?gro-2/89196 https://doi.org/10.5194/tc-15-3507-2021 en eng 1994-0424 Abteilung Strukturgeologie und Geodynamik Abteilung Computational Geoscience Geowissenschaftliches Zentrum Fakultät für Geowissenschaften und Geographie https://resolver.sub.uni-goettingen.de/purl?gro-2/89196 doi:10.5194/tc-15-3507-2021 CC BY 4.0 journal_article original_ja yes published_version 2021 ftsubgoettingen https://doi.org/10.5194/tc-15-3507-2021 2023-08-20T22:15:48Z Abstract. The crystal orientation fabric (COF) in ice cores provides detailed information, such as grain size and distribution and the orientation of the crystals in relation to the large-scale glacier flow. These data are relevant for a profound understanding of the dynamics and deformation history of glaciers and ice sheets. The intrinsic, mechanical anisotropy of the ice crystals causes an anisotropy of the polycrystalline ice of glaciers and affects the velocity of acoustic waves propagating through the ice. Here, we employ such acoustic waves to obtain the seismic anisotropy of ice core samples and compare the results with calculated acoustic velocities derived from COF analyses. These samples originate from an ice core from Rhonegletscher (Rhone Glacier), a temperate glacier in the Swiss Alps. Point-contact transducers transmit ultrasonic P waves with a dominant frequency of 1 MHz into the ice core samples and measure variations in the travel times of these waves for a set of azimuthal angles. In addition, the elasticity tensor is obtained from laboratory-measured COF, and we calculate the associated seismic velocities. We compare these COF-derived velocity profiles with the measured ultrasonic profiles. Especially in the presence of large ice grains, these two methods show significantly different velocities since the ultrasonic measurements examine a limited volume of the ice core, whereas the COF-derived velocities are integrated over larger parts of the core. This discrepancy between the ultrasonic and COF-derived profiles decreases with an increasing number of grains that are available within the sampling volume, and both methods provide consistent results in the presence of a similar amount of grains. We also explore the limitations of ultrasonic measurements and provide suggestions for improving their results. These ultrasonic measurements could be employed continuously along the ice cores. They are suitable to support the COF analyses by bridging the gaps between discrete measurements since these ... Article in Journal/Newspaper ice core Georg-August-Universität Göttingen: GoeScholar Rhone ENVELOPE(158.733,158.733,-79.983,-79.983) Rhone Glacier ENVELOPE(162.200,162.200,-77.667,-77.667) The Cryosphere 15 7 3507 3521
institution Open Polar
collection Georg-August-Universität Göttingen: GoeScholar
op_collection_id ftsubgoettingen
language English
description Abstract. The crystal orientation fabric (COF) in ice cores provides detailed information, such as grain size and distribution and the orientation of the crystals in relation to the large-scale glacier flow. These data are relevant for a profound understanding of the dynamics and deformation history of glaciers and ice sheets. The intrinsic, mechanical anisotropy of the ice crystals causes an anisotropy of the polycrystalline ice of glaciers and affects the velocity of acoustic waves propagating through the ice. Here, we employ such acoustic waves to obtain the seismic anisotropy of ice core samples and compare the results with calculated acoustic velocities derived from COF analyses. These samples originate from an ice core from Rhonegletscher (Rhone Glacier), a temperate glacier in the Swiss Alps. Point-contact transducers transmit ultrasonic P waves with a dominant frequency of 1 MHz into the ice core samples and measure variations in the travel times of these waves for a set of azimuthal angles. In addition, the elasticity tensor is obtained from laboratory-measured COF, and we calculate the associated seismic velocities. We compare these COF-derived velocity profiles with the measured ultrasonic profiles. Especially in the presence of large ice grains, these two methods show significantly different velocities since the ultrasonic measurements examine a limited volume of the ice core, whereas the COF-derived velocities are integrated over larger parts of the core. This discrepancy between the ultrasonic and COF-derived profiles decreases with an increasing number of grains that are available within the sampling volume, and both methods provide consistent results in the presence of a similar amount of grains. We also explore the limitations of ultrasonic measurements and provide suggestions for improving their results. These ultrasonic measurements could be employed continuously along the ice cores. They are suitable to support the COF analyses by bridging the gaps between discrete measurements since these ...
format Article in Journal/Newspaper
author Hellmann, Sebastian
Grab, Melchior
Kerch, Johanna
Löwe, Henning
Bauder, Andreas
Weikusat, Ilka
Maurer, Hansruedi
spellingShingle Hellmann, Sebastian
Grab, Melchior
Kerch, Johanna
Löwe, Henning
Bauder, Andreas
Weikusat, Ilka
Maurer, Hansruedi
Acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core
author_facet Hellmann, Sebastian
Grab, Melchior
Kerch, Johanna
Löwe, Henning
Bauder, Andreas
Weikusat, Ilka
Maurer, Hansruedi
author_sort Hellmann, Sebastian
title Acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core
title_short Acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core
title_full Acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core
title_fullStr Acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core
title_full_unstemmed Acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core
title_sort acoustic velocity measurements for detecting the crystal orientation fabrics of a temperate ice core
publishDate 2021
url https://resolver.sub.uni-goettingen.de/purl?gro-2/89196
https://doi.org/10.5194/tc-15-3507-2021
long_lat ENVELOPE(158.733,158.733,-79.983,-79.983)
ENVELOPE(162.200,162.200,-77.667,-77.667)
geographic Rhone
Rhone Glacier
geographic_facet Rhone
Rhone Glacier
genre ice core
genre_facet ice core
op_relation 1994-0424
Abteilung Strukturgeologie und Geodynamik
Abteilung Computational Geoscience
Geowissenschaftliches Zentrum
Fakultät für Geowissenschaften und Geographie
https://resolver.sub.uni-goettingen.de/purl?gro-2/89196
doi:10.5194/tc-15-3507-2021
op_rights CC BY 4.0
op_doi https://doi.org/10.5194/tc-15-3507-2021
container_title The Cryosphere
container_volume 15
container_issue 7
container_start_page 3507
op_container_end_page 3521
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