Variations in the Sliding of a Temperate Glacier
Detailed measurements of the positions of stakes along the center-line of the lower Nisqually Glacier were made over a period of two years. Variations in the basal sliding speed were calculated from the measured changes in surface speed, surface slope, and thickness, using the glacier flow model of...
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Language: | English |
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Cambridge University Press (CUP)
1974
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Online Access: | http://dx.doi.org/10.1017/s0022143000023157 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000023157 |
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crcambridgeupr:10.1017/s0022143000023157 2024-03-03T08:46:07+00:00 Variations in the Sliding of a Temperate Glacier Hodge, Steven M. 1974 http://dx.doi.org/10.1017/s0022143000023157 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000023157 en eng Cambridge University Press (CUP) Journal of Glaciology volume 13, issue 69, page 349-369 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1974 crcambridgeupr https://doi.org/10.1017/s0022143000023157 2024-02-08T08:36:10Z Detailed measurements of the positions of stakes along the center-line of the lower Nisqually Glacier were made over a period of two years. Variations in the basal sliding speed were calculated from the measured changes in surface speed, surface slope, and thickness, using the glacier flow model of Nye (1952) and allowing for the effect of the valley walls, longitudinal stress gradients, and uncertainties in the flow law of ice. The flow is predominantly by basal sliding and has a pronounced seasonal variation of approximately ±25%. Internal deformation contributes progressively less to the total motion with distance up-glacier. Neither the phase nor the magnitude of the seasonal velocity fluctuations can be accounted for by seasonal variations in the state of stress within the ice or at the bed, and the variations do not correlate directly with the melt-water discharge from the terminus. A seasonal wave in the ice flow travels down the glacier at a speed too high for propagation by internal deformation or the pressure melting/enhanced creep mechanism of basal sliding. The rate of sliding appears to be determined primarily by the amount of water in temporary storage in the glacier. The peak in sliding speed occurs, on the average, at the same time as the maximum liquid water storage of the South Cascade Glacier. The data support the idea that glaciers store water in the fall, winter and spring and then release it in the summer. This temporary storage may be greatest near the equilibrium line. The amount of stored water may increase over a period of years and be released catastrophically as a jökulhlaup. Any dependence of sliding on the basal shear stress is probably masked by the effect of variations in the hydrostatic pressure of water having access to the bed. Article in Journal/Newspaper Journal of Glaciology Cambridge University Press Cascade Glacier ENVELOPE(-140.504,-140.504,60.249,60.249) Journal of Glaciology 13 69 349 369 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Hodge, Steven M. Variations in the Sliding of a Temperate Glacier |
topic_facet |
Earth-Surface Processes |
description |
Detailed measurements of the positions of stakes along the center-line of the lower Nisqually Glacier were made over a period of two years. Variations in the basal sliding speed were calculated from the measured changes in surface speed, surface slope, and thickness, using the glacier flow model of Nye (1952) and allowing for the effect of the valley walls, longitudinal stress gradients, and uncertainties in the flow law of ice. The flow is predominantly by basal sliding and has a pronounced seasonal variation of approximately ±25%. Internal deformation contributes progressively less to the total motion with distance up-glacier. Neither the phase nor the magnitude of the seasonal velocity fluctuations can be accounted for by seasonal variations in the state of stress within the ice or at the bed, and the variations do not correlate directly with the melt-water discharge from the terminus. A seasonal wave in the ice flow travels down the glacier at a speed too high for propagation by internal deformation or the pressure melting/enhanced creep mechanism of basal sliding. The rate of sliding appears to be determined primarily by the amount of water in temporary storage in the glacier. The peak in sliding speed occurs, on the average, at the same time as the maximum liquid water storage of the South Cascade Glacier. The data support the idea that glaciers store water in the fall, winter and spring and then release it in the summer. This temporary storage may be greatest near the equilibrium line. The amount of stored water may increase over a period of years and be released catastrophically as a jökulhlaup. Any dependence of sliding on the basal shear stress is probably masked by the effect of variations in the hydrostatic pressure of water having access to the bed. |
format |
Article in Journal/Newspaper |
author |
Hodge, Steven M. |
author_facet |
Hodge, Steven M. |
author_sort |
Hodge, Steven M. |
title |
Variations in the Sliding of a Temperate Glacier |
title_short |
Variations in the Sliding of a Temperate Glacier |
title_full |
Variations in the Sliding of a Temperate Glacier |
title_fullStr |
Variations in the Sliding of a Temperate Glacier |
title_full_unstemmed |
Variations in the Sliding of a Temperate Glacier |
title_sort |
variations in the sliding of a temperate glacier |
publisher |
Cambridge University Press (CUP) |
publishDate |
1974 |
url |
http://dx.doi.org/10.1017/s0022143000023157 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000023157 |
long_lat |
ENVELOPE(-140.504,-140.504,60.249,60.249) |
geographic |
Cascade Glacier |
geographic_facet |
Cascade Glacier |
genre |
Journal of Glaciology |
genre_facet |
Journal of Glaciology |
op_source |
Journal of Glaciology volume 13, issue 69, page 349-369 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000023157 |
container_title |
Journal of Glaciology |
container_volume |
13 |
container_issue |
69 |
container_start_page |
349 |
op_container_end_page |
369 |
_version_ |
1792502024374321152 |