Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation
The data presented in part 1 of this paper (Meier et al., this issue) are here used to assess the role of water input/output, water storage, and basal water pressure in the rapid movement of Columbia Glacier, Alaska. Consistently high basal water pressures, mostly in the range from 300 kPa below to...
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American Geophysical Union
1994
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ftcaltechauth:oai:authors.library.caltech.edu:46598 2023-05-15T16:20:35+02:00 Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation Kamb, Barclay Engelhardt, Hermann Fahnestock, Mark Humphrey, Neil Meier, Mark Stone, Dan 1994-08-10 application/pdf https://authors.library.caltech.edu/46598/ https://authors.library.caltech.edu/46598/1/jgrb9542.pdf https://resolver.caltech.edu/CaltechAUTHORS:20140701-103209347 en eng American Geophysical Union https://authors.library.caltech.edu/46598/1/jgrb9542.pdf Kamb, Barclay and Engelhardt, Hermann and Fahnestock, Mark and Humphrey, Neil and Meier, Mark and Stone, Dan (1994) Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation. Journal of Geophysical Research B, 99 (B8). pp. 15231-15244. ISSN 0148-0227. doi:10.1029/94JB00467. https://resolver.caltech.edu/CaltechAUTHORS:20140701-103209347 <https://resolver.caltech.edu/CaltechAUTHORS:20140701-103209347> other Article PeerReviewed 1994 ftcaltechauth https://doi.org/10.1029/94JB00467 2021-11-11T18:58:23Z The data presented in part 1 of this paper (Meier et al., this issue) are here used to assess the role of water input/output, water storage, and basal water pressure in the rapid movement of Columbia Glacier, Alaska. Consistently high basal water pressures, mostly in the range from 300 kPa below to 100 kPa above the ice overburden pressure, are responsible in an overall way for the high glacier flow velocities (3.5–9 m d^−1), which are due mainly to rapid basal sliding caused by the high water pressure. Diurnal fluctuation in basal water pressure is accompanied by fluctuation in sliding velocity in what appears to be a direct causal relation at the upglacier observation site. The water pressure fluctuation tracks the time-integrated water input (less a steady withdrawal), as expected for the diurnally fluctuating storage of water in the glacier far from the terminus. At the downglacier site, the situation is more complex. Diurnal peaks in water level, which are directly related to intraglacial water storage as well as to basal water pressure, are shifted forward in time by 4 hours, probably as a result of the effect of diurnal fluctuation in water output from the glacier, which affects the local water storage fluctuations near the terminus. Because of the forward shift in the basal water pressure peaks, which at the downglacier site lead the velocity peaks by 6 hours, a mechanical connection between water pressure and sliding there would have to involve a 6-hour (quarter period) delay. However, the nearly identical nature of the diurnal fluctuations in velocity at the two sites argues for a single, consistent control mechanism at both sites. The velocity variations in nondiurnal “speed-up events” caused by extra input of water on the longer timescale of several days are only obscurely if at all correlated with variations in basal water pressure but correlate well with water storage in the glacier. It appears that small variations in water pressure (≤100 kPa) sufficient to produce the observed velocity variations (15–30%) are mostly masked by pressure fluctuations caused by spontaneous local reorganizations of the basal water conduit system on a spatial scale much smaller than the longitudinal coupling length over which basal water pressure is effectively averaged in determining the sliding velocity. At the achieved level of observation the clearest (though not complication free) control variable for the sliding velocity variations is basal water storage by cavitation at the glacier bed. Article in Journal/Newspaper glacier Tidewater Alaska Caltech Authors (California Institute of Technology) Meier ENVELOPE(-45.900,-45.900,-60.633,-60.633) Journal of Geophysical Research 99 B8 15231 |
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Open Polar |
collection |
Caltech Authors (California Institute of Technology) |
op_collection_id |
ftcaltechauth |
language |
English |
description |
The data presented in part 1 of this paper (Meier et al., this issue) are here used to assess the role of water input/output, water storage, and basal water pressure in the rapid movement of Columbia Glacier, Alaska. Consistently high basal water pressures, mostly in the range from 300 kPa below to 100 kPa above the ice overburden pressure, are responsible in an overall way for the high glacier flow velocities (3.5–9 m d^−1), which are due mainly to rapid basal sliding caused by the high water pressure. Diurnal fluctuation in basal water pressure is accompanied by fluctuation in sliding velocity in what appears to be a direct causal relation at the upglacier observation site. The water pressure fluctuation tracks the time-integrated water input (less a steady withdrawal), as expected for the diurnally fluctuating storage of water in the glacier far from the terminus. At the downglacier site, the situation is more complex. Diurnal peaks in water level, which are directly related to intraglacial water storage as well as to basal water pressure, are shifted forward in time by 4 hours, probably as a result of the effect of diurnal fluctuation in water output from the glacier, which affects the local water storage fluctuations near the terminus. Because of the forward shift in the basal water pressure peaks, which at the downglacier site lead the velocity peaks by 6 hours, a mechanical connection between water pressure and sliding there would have to involve a 6-hour (quarter period) delay. However, the nearly identical nature of the diurnal fluctuations in velocity at the two sites argues for a single, consistent control mechanism at both sites. The velocity variations in nondiurnal “speed-up events” caused by extra input of water on the longer timescale of several days are only obscurely if at all correlated with variations in basal water pressure but correlate well with water storage in the glacier. It appears that small variations in water pressure (≤100 kPa) sufficient to produce the observed velocity variations (15–30%) are mostly masked by pressure fluctuations caused by spontaneous local reorganizations of the basal water conduit system on a spatial scale much smaller than the longitudinal coupling length over which basal water pressure is effectively averaged in determining the sliding velocity. At the achieved level of observation the clearest (though not complication free) control variable for the sliding velocity variations is basal water storage by cavitation at the glacier bed. |
format |
Article in Journal/Newspaper |
author |
Kamb, Barclay Engelhardt, Hermann Fahnestock, Mark Humphrey, Neil Meier, Mark Stone, Dan |
spellingShingle |
Kamb, Barclay Engelhardt, Hermann Fahnestock, Mark Humphrey, Neil Meier, Mark Stone, Dan Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation |
author_facet |
Kamb, Barclay Engelhardt, Hermann Fahnestock, Mark Humphrey, Neil Meier, Mark Stone, Dan |
author_sort |
Kamb, Barclay |
title |
Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation |
title_short |
Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation |
title_full |
Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation |
title_fullStr |
Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation |
title_full_unstemmed |
Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation |
title_sort |
mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. interpretation |
publisher |
American Geophysical Union |
publishDate |
1994 |
url |
https://authors.library.caltech.edu/46598/ https://authors.library.caltech.edu/46598/1/jgrb9542.pdf https://resolver.caltech.edu/CaltechAUTHORS:20140701-103209347 |
long_lat |
ENVELOPE(-45.900,-45.900,-60.633,-60.633) |
geographic |
Meier |
geographic_facet |
Meier |
genre |
glacier Tidewater Alaska |
genre_facet |
glacier Tidewater Alaska |
op_relation |
https://authors.library.caltech.edu/46598/1/jgrb9542.pdf Kamb, Barclay and Engelhardt, Hermann and Fahnestock, Mark and Humphrey, Neil and Meier, Mark and Stone, Dan (1994) Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation. Journal of Geophysical Research B, 99 (B8). pp. 15231-15244. ISSN 0148-0227. doi:10.1029/94JB00467. https://resolver.caltech.edu/CaltechAUTHORS:20140701-103209347 <https://resolver.caltech.edu/CaltechAUTHORS:20140701-103209347> |
op_rights |
other |
op_doi |
https://doi.org/10.1029/94JB00467 |
container_title |
Journal of Geophysical Research |
container_volume |
99 |
container_issue |
B8 |
container_start_page |
15231 |
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1766008507260207104 |