Continuous profiles of electromagnetic wave velocity and water content in glaciers: an example from Bench Glacier, Alaska, USA
We conducted two-dimensional continuous multi-offset georadar surveys on Bench Glacier, south-central Alaska, USA, to measure the distribution of englacial water. We acquired data with a multi channel 25 MHz radar system using transmitter-receiver offsets ranging from 5 to 150 m. We towed the radar...
| Published in: | Annals of Glaciology |
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| Main Authors: | , , , |
| Format: | Text |
| Language: | unknown |
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ScholarWorks at University of Montana
2009
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| Subjects: | |
| Online Access: | https://scholarworks.umt.edu/geosci_pubs/36 https://doi.org/10.3189/172756409789097540 https://scholarworks.umt.edu/context/geosci_pubs/article/1038/viewcontent/watercontent_annals09.pdf |
| Summary: | We conducted two-dimensional continuous multi-offset georadar surveys on Bench Glacier, south-central Alaska, USA, to measure the distribution of englacial water. We acquired data with a multi channel 25 MHz radar system using transmitter-receiver offsets ranging from 5 to 150 m. We towed the radar system at 5-10 kmh-1 with a snow machine with transmitter/receiver positions established by geodetic-grade kinematic deferentially corrected GPS (nominal 0.5 m trace spacing). For radar velocity analyses, we employed reflection tomography in the pre-stack depth-migrated domain to attain an estimated 2% velocity uncertainty when averaged over three to five wavelengths. We estimated water content from the velocity structure using the complex refractive index method equation and use a three-phase model (ice, water, air) that accounts for compression of air bubbles as a function of depth. Our analysis produced laterally continuous profiles of glacier water content over several kilometers. These profiles show a laterally variable, stratified velocity structure with a low-water-content (about 0-0.5%) shallow layer (about 20-30 m) underlain by high-water-content (1-2.5%) ice. |
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