Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier
Funder: Aberystwyth University Capital Equipment Fund <jats:title>Abstract</jats:title><jats:p>Optical televiewer borehole logging within a crevassed region of fast‐moving Store Glacier, Greenland, revealed the presence of 35 high‐angle planes that cut across the background primary...
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ftunivcam:oai:www.repository.cam.ac.uk:1810/323384 2023-10-29T02:36:29+01:00 Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier Hubbard, Bryn Christoffersen, Poul Doyle, Samuel H Chudley, Thomas R Schoonman, Charlotte M Law, Robert Bougamont, Marion 2021-06-04T13:53:56Z application/pdf text/xml https://www.repository.cam.ac.uk/handle/1810/323384 https://doi.org/10.17863/CAM.70842 en eng American Geophysical Union (AGU) http://dx.doi.org/10.1029/2020av000291 AGU ADVANCES https://www.repository.cam.ac.uk/handle/1810/323384 doi:10.17863/CAM.70842 borehole crevasse deep crevasse glacier Greenland Ice Sheet optical televiewer Article 2021 ftunivcam https://doi.org/10.17863/CAM.70842 2023-10-05T22:19:28Z Funder: Aberystwyth University Capital Equipment Fund <jats:title>Abstract</jats:title><jats:p>Optical televiewer borehole logging within a crevassed region of fast‐moving Store Glacier, Greenland, revealed the presence of 35 high‐angle planes that cut across the background primary stratification. These planes were composed of a bubble‐free layer of refrozen ice, most of which hosted thin laminae of bubble‐rich “last frozen” ice, consistent with the planes being the traces of former open crevasses. Several such last‐frozen laminae were observed in four traces, suggesting multiple episodes of crevasse reactivation. The frequency of crevasse traces generally decreased with depth, with the deepest detectable trace being 265 m below the surface. This is consistent with the extent of the warmer‐than‐modeled englacial ice layer in the area, which extends from the surface to a depth of ∼400 m. Crevasse trace orientation was strongly clustered around a dip of 63° and a strike that was offset by 71° from orthogonal to the local direction of principal extending strain. The traces’ antecedent crevasses were therefore interpreted to have originated upglacier, probably ∼8 km distant involving mixed‐mode (I and III) formation. We conclude that deep crevassing is pervasive across Store Glacier, and therefore also at all dynamically similar outlet glaciers. Once healed, their traces represent planes of weakness subject to reactivation during subsequent advection through the glacier. Given their depth, it is highly likely that such traces—particularly those formed downglacier—survive surface ablation to reach the glacier terminus, where they may represent foci for fracture and iceberg calving.</jats:p> Article in Journal/Newspaper glacier Greenland greenlandic Ice Sheet Apollo - University of Cambridge Repository |
institution |
Open Polar |
collection |
Apollo - University of Cambridge Repository |
op_collection_id |
ftunivcam |
language |
English |
topic |
borehole crevasse deep crevasse glacier Greenland Ice Sheet optical televiewer |
spellingShingle |
borehole crevasse deep crevasse glacier Greenland Ice Sheet optical televiewer Hubbard, Bryn Christoffersen, Poul Doyle, Samuel H Chudley, Thomas R Schoonman, Charlotte M Law, Robert Bougamont, Marion Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier |
topic_facet |
borehole crevasse deep crevasse glacier Greenland Ice Sheet optical televiewer |
description |
Funder: Aberystwyth University Capital Equipment Fund <jats:title>Abstract</jats:title><jats:p>Optical televiewer borehole logging within a crevassed region of fast‐moving Store Glacier, Greenland, revealed the presence of 35 high‐angle planes that cut across the background primary stratification. These planes were composed of a bubble‐free layer of refrozen ice, most of which hosted thin laminae of bubble‐rich “last frozen” ice, consistent with the planes being the traces of former open crevasses. Several such last‐frozen laminae were observed in four traces, suggesting multiple episodes of crevasse reactivation. The frequency of crevasse traces generally decreased with depth, with the deepest detectable trace being 265 m below the surface. This is consistent with the extent of the warmer‐than‐modeled englacial ice layer in the area, which extends from the surface to a depth of ∼400 m. Crevasse trace orientation was strongly clustered around a dip of 63° and a strike that was offset by 71° from orthogonal to the local direction of principal extending strain. The traces’ antecedent crevasses were therefore interpreted to have originated upglacier, probably ∼8 km distant involving mixed‐mode (I and III) formation. We conclude that deep crevassing is pervasive across Store Glacier, and therefore also at all dynamically similar outlet glaciers. Once healed, their traces represent planes of weakness subject to reactivation during subsequent advection through the glacier. Given their depth, it is highly likely that such traces—particularly those formed downglacier—survive surface ablation to reach the glacier terminus, where they may represent foci for fracture and iceberg calving.</jats:p> |
format |
Article in Journal/Newspaper |
author |
Hubbard, Bryn Christoffersen, Poul Doyle, Samuel H Chudley, Thomas R Schoonman, Charlotte M Law, Robert Bougamont, Marion |
author_facet |
Hubbard, Bryn Christoffersen, Poul Doyle, Samuel H Chudley, Thomas R Schoonman, Charlotte M Law, Robert Bougamont, Marion |
author_sort |
Hubbard, Bryn |
title |
Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier |
title_short |
Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier |
title_full |
Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier |
title_fullStr |
Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier |
title_full_unstemmed |
Borehole-Based Characterization of Deep Mixed-Mode Crevasses at a Greenlandic Outlet Glacier |
title_sort |
borehole-based characterization of deep mixed-mode crevasses at a greenlandic outlet glacier |
publisher |
American Geophysical Union (AGU) |
publishDate |
2021 |
url |
https://www.repository.cam.ac.uk/handle/1810/323384 https://doi.org/10.17863/CAM.70842 |
genre |
glacier Greenland greenlandic Ice Sheet |
genre_facet |
glacier Greenland greenlandic Ice Sheet |
op_relation |
https://www.repository.cam.ac.uk/handle/1810/323384 doi:10.17863/CAM.70842 |
op_doi |
https://doi.org/10.17863/CAM.70842 |
_version_ |
1781060441270648832 |