Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska
Abstract Radio-echo returns from internal reflectors were monitored for three weeks during surge motion on Variegated Glacier, Alaska in July 1982. A monopulse transmitter with 3 MHz center frequency was fixed on the glacier surface near the equilibrium line. Data were recorded on magnetic tape appr...
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Cambridge University Press (CUP)
1984
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Online Access: | http://dx.doi.org/10.1017/s0022143000008443 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000008443 |
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crcambridgeupr:10.1017/s0022143000008443 2024-03-03T08:44:34+00:00 Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska Jacobel, Robert Raymond, Charles 1984 http://dx.doi.org/10.1017/s0022143000008443 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000008443 en eng Cambridge University Press (CUP) Journal of Glaciology volume 30, issue 104, page 22-29 ISSN 0022-1430 1727-5652 Earth-Surface Processes journal-article 1984 crcambridgeupr https://doi.org/10.1017/s0022143000008443 2024-02-08T08:32:56Z Abstract Radio-echo returns from internal reflectors were monitored for three weeks during surge motion on Variegated Glacier, Alaska in July 1982. A monopulse transmitter with 3 MHz center frequency was fixed on the glacier surface near the equilibrium line. Data were recorded on magnetic tape approximately three times daily and contain both amplitude and phase information. The frequency spectrum of returned radiation from englacial scatterers shows peaks in the 12 to 30 MHz range which places constraints on the size and geometry of the scatterers. Timing of variations in the amplitude and frequency of returned radiation were found to coincide with changes in glacier velocity, basal water pressure, and surface melt rate. These changes in the echo pattern are interpreted in terms of the redistribution of water in englacial channels and cavities connected to the bed some distance down-glacier. This connection has large hydraulic resistance compared to a bore hole connected vertically to the bed. The inflow of water to the cavities from surface melt and rain and the drainage are generally in equilibrium except in times of changed surface input and during surge pulses. In the latter case, water may fill these cavities due to increased pressure at the bed associated with the motion pulse. The information obtained is therefore complementary to bore-hole water pressure levels but cannot duplicate it. This is apparently due to fundamental differences in the hydraulics of the natural cavity and conduit system, and a bore hole connected vertically to the bed. Article in Journal/Newspaper glacier Journal of Glaciology Alaska Cambridge University Press Journal of Glaciology 30 104 22 29 |
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Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
topic |
Earth-Surface Processes |
spellingShingle |
Earth-Surface Processes Jacobel, Robert Raymond, Charles Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska |
topic_facet |
Earth-Surface Processes |
description |
Abstract Radio-echo returns from internal reflectors were monitored for three weeks during surge motion on Variegated Glacier, Alaska in July 1982. A monopulse transmitter with 3 MHz center frequency was fixed on the glacier surface near the equilibrium line. Data were recorded on magnetic tape approximately three times daily and contain both amplitude and phase information. The frequency spectrum of returned radiation from englacial scatterers shows peaks in the 12 to 30 MHz range which places constraints on the size and geometry of the scatterers. Timing of variations in the amplitude and frequency of returned radiation were found to coincide with changes in glacier velocity, basal water pressure, and surface melt rate. These changes in the echo pattern are interpreted in terms of the redistribution of water in englacial channels and cavities connected to the bed some distance down-glacier. This connection has large hydraulic resistance compared to a bore hole connected vertically to the bed. The inflow of water to the cavities from surface melt and rain and the drainage are generally in equilibrium except in times of changed surface input and during surge pulses. In the latter case, water may fill these cavities due to increased pressure at the bed associated with the motion pulse. The information obtained is therefore complementary to bore-hole water pressure levels but cannot duplicate it. This is apparently due to fundamental differences in the hydraulics of the natural cavity and conduit system, and a bore hole connected vertically to the bed. |
format |
Article in Journal/Newspaper |
author |
Jacobel, Robert Raymond, Charles |
author_facet |
Jacobel, Robert Raymond, Charles |
author_sort |
Jacobel, Robert |
title |
Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska |
title_short |
Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska |
title_full |
Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska |
title_fullStr |
Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska |
title_full_unstemmed |
Radio Echo-Sounding Studies of Englacial Water Movement in Variegated Glacier, Alaska |
title_sort |
radio echo-sounding studies of englacial water movement in variegated glacier, alaska |
publisher |
Cambridge University Press (CUP) |
publishDate |
1984 |
url |
http://dx.doi.org/10.1017/s0022143000008443 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000008443 |
genre |
glacier Journal of Glaciology Alaska |
genre_facet |
glacier Journal of Glaciology Alaska |
op_source |
Journal of Glaciology volume 30, issue 104, page 22-29 ISSN 0022-1430 1727-5652 |
op_doi |
https://doi.org/10.1017/s0022143000008443 |
container_title |
Journal of Glaciology |
container_volume |
30 |
container_issue |
104 |
container_start_page |
22 |
op_container_end_page |
29 |
_version_ |
1792500058299564032 |