Physical Conditions of Fast Glacier Flow:2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland
Outlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because discharge and ablation often exceed the accumulation. To develop a better understanding of these fast-flowing glaciers, we investigate the basal conditions of Sto...
Published in: | Journal of Geophysical Research: Earth Surface |
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Main Authors: | , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
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2018
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Online Access: | https://research-portal.st-andrews.ac.uk/en/researchoutput/physical-conditions-of-fast-glacier-flow(d8aa1282-4744-4bfb-9dd3-07d665981547).html https://doi.org/10.1002/2017JF004297 http://www.scopus.com/inward/record.url?scp=85042441998&partnerID=8YFLogxK |
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ftunstandrewcris:oai:research-portal.st-andrews.ac.uk:publications/d8aa1282-4744-4bfb-9dd3-07d665981547 2024-09-09T19:41:20+00:00 Physical Conditions of Fast Glacier Flow:2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland Hofstede, C. Christoffersen, P. Hubbard, B. Doyle, S. H. Young, T. J. Diez, A. Eisen, O. Hubbard, A. 2018-02 https://research-portal.st-andrews.ac.uk/en/researchoutput/physical-conditions-of-fast-glacier-flow(d8aa1282-4744-4bfb-9dd3-07d665981547).html https://doi.org/10.1002/2017JF004297 http://www.scopus.com/inward/record.url?scp=85042441998&partnerID=8YFLogxK eng eng https://research-portal.st-andrews.ac.uk/en/researchoutput/physical-conditions-of-fast-glacier-flow(d8aa1282-4744-4bfb-9dd3-07d665981547).html info:eu-repo/semantics/openAccess Hofstede , C , Christoffersen , P , Hubbard , B , Doyle , S H , Young , T J , Diez , A , Eisen , O & Hubbard , A 2018 , ' Physical Conditions of Fast Glacier Flow : 2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland ' , Journal of Geophysical Research: Earth Surface , vol. 123 , no. 2 , pp. 349-362 . https://doi.org/10.1002/2017JF004297 anisotropy deformation patches seismic sliding subglacial article 2018 ftunstandrewcris https://doi.org/10.1002/2017JF004297 2024-06-19T23:54:29Z Outlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because discharge and ablation often exceed the accumulation. To develop a better understanding of these fast-flowing glaciers, we investigate the basal conditions of Store Glacier, a large outlet glacier flowing into Uummannaq Fjord in west Greenland. We use two crossing seismic profiles acquired near the centerline, 30 km upstream of the calving front, to interpret the physical nature of the ice and bed. We identify one notably englacial and two notably subglacial seismic reflections on both profiles. The englacial reflection represents a change in crystal orientation fabric, interpreted to be the Holocene-Wisconsin transition. From Amplitude-Versus-Angle (AVA) analysis we infer that the deepest ∼80 m of ice of the parallel-flow profile below this reflection is anisotropic with an enhancement of simple shear of ∼2. The ice is underlain by ∼45 m of unconsolidated sediments, below which there is a strong reflection caused by the transition to consolidated sediments. In the across-flow profile subglacial properties vary over small scale and the polarity of the ice-bed reflection switches from positive to negative. We interpret these as patches of different basal slipperiness associated with variable amounts of water. Our results illustrate variability in basal properties, and hence ice-bed coupling, at a spatial scale of ∼100 m, highlighting the need for direct observations of the bed to improve the basal boundary conditions in ice-dynamic models. Article in Journal/Newspaper glacier Greenland Ice Sheet Uummannaq University of St Andrews: Research Portal Greenland Uummannaq Fjord ENVELOPE(-52.968,-52.968,70.925,70.925) Journal of Geophysical Research: Earth Surface 123 2 349 362 |
institution |
Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
topic |
anisotropy deformation patches seismic sliding subglacial |
spellingShingle |
anisotropy deformation patches seismic sliding subglacial Hofstede, C. Christoffersen, P. Hubbard, B. Doyle, S. H. Young, T. J. Diez, A. Eisen, O. Hubbard, A. Physical Conditions of Fast Glacier Flow:2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland |
topic_facet |
anisotropy deformation patches seismic sliding subglacial |
description |
Outlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because discharge and ablation often exceed the accumulation. To develop a better understanding of these fast-flowing glaciers, we investigate the basal conditions of Store Glacier, a large outlet glacier flowing into Uummannaq Fjord in west Greenland. We use two crossing seismic profiles acquired near the centerline, 30 km upstream of the calving front, to interpret the physical nature of the ice and bed. We identify one notably englacial and two notably subglacial seismic reflections on both profiles. The englacial reflection represents a change in crystal orientation fabric, interpreted to be the Holocene-Wisconsin transition. From Amplitude-Versus-Angle (AVA) analysis we infer that the deepest ∼80 m of ice of the parallel-flow profile below this reflection is anisotropic with an enhancement of simple shear of ∼2. The ice is underlain by ∼45 m of unconsolidated sediments, below which there is a strong reflection caused by the transition to consolidated sediments. In the across-flow profile subglacial properties vary over small scale and the polarity of the ice-bed reflection switches from positive to negative. We interpret these as patches of different basal slipperiness associated with variable amounts of water. Our results illustrate variability in basal properties, and hence ice-bed coupling, at a spatial scale of ∼100 m, highlighting the need for direct observations of the bed to improve the basal boundary conditions in ice-dynamic models. |
format |
Article in Journal/Newspaper |
author |
Hofstede, C. Christoffersen, P. Hubbard, B. Doyle, S. H. Young, T. J. Diez, A. Eisen, O. Hubbard, A. |
author_facet |
Hofstede, C. Christoffersen, P. Hubbard, B. Doyle, S. H. Young, T. J. Diez, A. Eisen, O. Hubbard, A. |
author_sort |
Hofstede, C. |
title |
Physical Conditions of Fast Glacier Flow:2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland |
title_short |
Physical Conditions of Fast Glacier Flow:2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland |
title_full |
Physical Conditions of Fast Glacier Flow:2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland |
title_fullStr |
Physical Conditions of Fast Glacier Flow:2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland |
title_full_unstemmed |
Physical Conditions of Fast Glacier Flow:2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland |
title_sort |
physical conditions of fast glacier flow:2. variable extent of anisotropic ice and soft basal sediment from seismic reflection data acquired on store glacier, west greenland |
publishDate |
2018 |
url |
https://research-portal.st-andrews.ac.uk/en/researchoutput/physical-conditions-of-fast-glacier-flow(d8aa1282-4744-4bfb-9dd3-07d665981547).html https://doi.org/10.1002/2017JF004297 http://www.scopus.com/inward/record.url?scp=85042441998&partnerID=8YFLogxK |
long_lat |
ENVELOPE(-52.968,-52.968,70.925,70.925) |
geographic |
Greenland Uummannaq Fjord |
geographic_facet |
Greenland Uummannaq Fjord |
genre |
glacier Greenland Ice Sheet Uummannaq |
genre_facet |
glacier Greenland Ice Sheet Uummannaq |
op_source |
Hofstede , C , Christoffersen , P , Hubbard , B , Doyle , S H , Young , T J , Diez , A , Eisen , O & Hubbard , A 2018 , ' Physical Conditions of Fast Glacier Flow : 2. Variable Extent of Anisotropic Ice and Soft Basal Sediment From Seismic Reflection Data Acquired on Store Glacier, West Greenland ' , Journal of Geophysical Research: Earth Surface , vol. 123 , no. 2 , pp. 349-362 . https://doi.org/10.1002/2017JF004297 |
op_relation |
https://research-portal.st-andrews.ac.uk/en/researchoutput/physical-conditions-of-fast-glacier-flow(d8aa1282-4744-4bfb-9dd3-07d665981547).html |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1002/2017JF004297 |
container_title |
Journal of Geophysical Research: Earth Surface |
container_volume |
123 |
container_issue |
2 |
container_start_page |
349 |
op_container_end_page |
362 |
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1809910747096940544 |