Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A.
Abstract Wire strain meters and seismometers spaced longitudinally along the upper part of Variegated Glacier, Alaska, showed quasi-periodic episodes of increased velocity (mini-surges), which lasted about 1 day and recurred at intervals of a few days to 2 weeks during the early part of the melt sea...
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Language: | English |
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Cambridge University Press (CUP)
1986
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Online Access: | http://dx.doi.org/10.1017/s0022143000015495 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000015495 |
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crcambridgeupr:10.1017/s0022143000015495 2024-03-03T08:44:34+00:00 Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A. Raymond, Charles F. Malone, Stephen 1986 http://dx.doi.org/10.1017/s0022143000015495 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000015495 en eng Cambridge University Press (CUP) Journal of Glaciology volume 32, issue 111, page 178-191 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1986 crcambridgeupr https://doi.org/10.1017/s0022143000015495 2024-02-08T08:37:11Z Abstract Wire strain meters and seismometers spaced longitudinally along the upper part of Variegated Glacier, Alaska, showed quasi-periodic episodes of increased velocity (mini-surges), which lasted about 1 day and recurred at intervals of a few days to 2 weeks during the early part of the melt seasons of 1979, 1980, and 1981. The zone affected by these mini-surges corresponds to the zone of highest velocity and basal stress increase over the previous decade, and the initiation of the most recent surge in 1982. Mini-surges initiate locally; as a single melt season progresses, the later mini-surges start at higher locations and show a distinct down-glacier propagation of a characteristic strain pattern and associated zone of acoustic emissions at speeds of 0.1–0.6 km h −1 . During mini-surges, extensile and compressive strain-rates exceed 10 × 10 −4 d −1 and 40 × 10 −4 d −1 , respectively; typical strain-rates between mini-surges were less than 2 × 10 −4 d −1 in magnitude. Seismic activity jumped by two orders of magnitude and was distinctly audible during a mini-surge. Maximum strain-rate during mini-surges decreased from year to year. The high time resolution of the strain allows short time-scale structure of velocity variations to be deduced. As a propagating mini-surge passes, the velocity anomaly at a fixed location is characterized by a rapid initial rise over a few hours to two distinct peaks separated by a few hours, followed by a slower return to normal velocity taking up to a day. The double peak in velocity may arise from a single, very sharp, transient peak in the basal slip velocity associated with the initial opening of cavities at the base in response to a sudden rise in basal water pressure (observed by Kamb and Engelhardt). This supports an important role for basal cavitation in the mini-surge mechanism. Article in Journal/Newspaper glacier Journal of Glaciology Alaska Cambridge University Press Journal of Glaciology 32 111 178 191 |
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Open Polar |
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Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Raymond, Charles F. Malone, Stephen Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A. |
topic_facet |
Earth-Surface Processes |
description |
Abstract Wire strain meters and seismometers spaced longitudinally along the upper part of Variegated Glacier, Alaska, showed quasi-periodic episodes of increased velocity (mini-surges), which lasted about 1 day and recurred at intervals of a few days to 2 weeks during the early part of the melt seasons of 1979, 1980, and 1981. The zone affected by these mini-surges corresponds to the zone of highest velocity and basal stress increase over the previous decade, and the initiation of the most recent surge in 1982. Mini-surges initiate locally; as a single melt season progresses, the later mini-surges start at higher locations and show a distinct down-glacier propagation of a characteristic strain pattern and associated zone of acoustic emissions at speeds of 0.1–0.6 km h −1 . During mini-surges, extensile and compressive strain-rates exceed 10 × 10 −4 d −1 and 40 × 10 −4 d −1 , respectively; typical strain-rates between mini-surges were less than 2 × 10 −4 d −1 in magnitude. Seismic activity jumped by two orders of magnitude and was distinctly audible during a mini-surge. Maximum strain-rate during mini-surges decreased from year to year. The high time resolution of the strain allows short time-scale structure of velocity variations to be deduced. As a propagating mini-surge passes, the velocity anomaly at a fixed location is characterized by a rapid initial rise over a few hours to two distinct peaks separated by a few hours, followed by a slower return to normal velocity taking up to a day. The double peak in velocity may arise from a single, very sharp, transient peak in the basal slip velocity associated with the initial opening of cavities at the base in response to a sudden rise in basal water pressure (observed by Kamb and Engelhardt). This supports an important role for basal cavitation in the mini-surge mechanism. |
format |
Article in Journal/Newspaper |
author |
Raymond, Charles F. Malone, Stephen |
author_facet |
Raymond, Charles F. Malone, Stephen |
author_sort |
Raymond, Charles F. |
title |
Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A. |
title_short |
Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A. |
title_full |
Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A. |
title_fullStr |
Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A. |
title_full_unstemmed |
Propagating Strain Anomalies during Mini-Surges of Variegated Glacier, Alaska, U.S.A. |
title_sort |
propagating strain anomalies during mini-surges of variegated glacier, alaska, u.s.a. |
publisher |
Cambridge University Press (CUP) |
publishDate |
1986 |
url |
http://dx.doi.org/10.1017/s0022143000015495 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000015495 |
genre |
glacier Journal of Glaciology Alaska |
genre_facet |
glacier Journal of Glaciology Alaska |
op_source |
Journal of Glaciology volume 32, issue 111, page 178-191 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000015495 |
container_title |
Journal of Glaciology |
container_volume |
32 |
container_issue |
111 |
container_start_page |
178 |
op_container_end_page |
191 |
_version_ |
1792500071202291712 |