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 because discharge and ablation often exceed the accumulation. To develop a better understanding of these fast flowing glaciers, we investigate the basal condition...
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ftunivcam:oai:www.repository.cam.ac.uk:1810/274391 2024-01-14T10:07:01+01:00 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, Coen Christoffersen, P Hubbard, Bryn Doyle, Samuel Young, Tun Jan Diez, Anja Eisen, Olaf Hubbard, Alun 2018 application/pdf https://www.repository.cam.ac.uk/handle/1810/274391 https://doi.org/10.17863/CAM.21073 eng eng Wiley-Blackwell http://dx.doi.org/10.1002/2017jf004297 Journal of Geophysical Research - Earth Surface https://www.repository.cam.ac.uk/handle/1810/274391 doi:10.17863/CAM.21073 Attribution 4.0 International http://creativecommons.org/licenses/by/4.0/ subglacial sliding deformation anisotropy patches seismic Article 2018 ftunivcam https://doi.org/10.17863/CAM.21073 2023-12-21T23:26:08Z Outlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because 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 centreline, 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 Apollo - University of Cambridge Repository Greenland Uummannaq Fjord ENVELOPE(-52.968,-52.968,70.925,70.925) |
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Open Polar |
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Apollo - University of Cambridge Repository |
op_collection_id |
ftunivcam |
language |
English |
topic |
subglacial sliding deformation anisotropy patches seismic |
spellingShingle |
subglacial sliding deformation anisotropy patches seismic Hofstede, Coen Christoffersen, P Hubbard, Bryn Doyle, Samuel Young, Tun Jan Diez, Anja Eisen, Olaf Hubbard, Alun 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 |
subglacial sliding deformation anisotropy patches seismic |
description |
Outlet glaciers of the Greenland Ice Sheet transport ice from the interior to the ocean and contribute directly to sea level rise because 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 centreline, 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, Coen Christoffersen, P Hubbard, Bryn Doyle, Samuel Young, Tun Jan Diez, Anja Eisen, Olaf Hubbard, Alun |
author_facet |
Hofstede, Coen Christoffersen, P Hubbard, Bryn Doyle, Samuel Young, Tun Jan Diez, Anja Eisen, Olaf Hubbard, Alun |
author_sort |
Hofstede, Coen |
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 |
publisher |
Wiley-Blackwell |
publishDate |
2018 |
url |
https://www.repository.cam.ac.uk/handle/1810/274391 https://doi.org/10.17863/CAM.21073 |
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_relation |
https://www.repository.cam.ac.uk/handle/1810/274391 doi:10.17863/CAM.21073 |
op_rights |
Attribution 4.0 International http://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.17863/CAM.21073 |
_version_ |
1788061430515236864 |