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https://hdl.handle.net/11681/9423| Title: | Electromagnetic measurements of multi-year sea ice using impulse radar |
| Authors: | United States. Department of Energy. Kovacs, Austin. Morey, Rexford M. |
| Keywords: | Cold regions Electromagetic properties Electromagnetic measurements Impulse radar Radar Marine geophysics Geophysics Ice Sea ice Sea ice measurement Dielectrics Hydrology |
| Publisher: | Cold Regions Research and Engineering Laboratory (U.S.) Engineer Research and Development Center (U.S.) |
| Series/Report no.: | CRREL report ; 85-13. |
| Description: | CRREL Report Abstract: Sounding of multi-year sea ice, using impulse radar operating in the 80- to 500-MHz frequency band, has revealed that the bottom of this ice cannot always be detected. This paper discusses a field program aimed at finding out why this is so, and at determining the electromagnetic (EM) properties of multi-year sea ice. It was found that the bottom of the ice could not be detected when the ice structure had a high brine content. Because of brlne's high conductivity, brine volume dominates the loss mechanism in first-year sea ice, and the same was found true for multi-year ice. A two-phase dielectric mixing formula. used by the authors to describe the EM properties of first-year sea ice, was modified to include the effects of the gas pockets found in the multi-year sea ice. This three-phase mixture model was found to estimate the EM properties of the multi-year ice studied over the frequency band of interest. The latter values were determined by: 1) vertical sounding to a subsurface target of known depth, where the two-way travel time of the EM wavelet in the ice is measured; 2) cross-borehole transmission. where the transit time of the EM wavelet is measured through a known thickness of sea ice; and 3) a wide-angle or common-depth-polnt reflection method. Preliminary findings also indicate that a representative value for the apparent bulk dielectric constant of multi-year sea ice over 2 and 1/2 m thick is 3.5. This represents an effective EM wavelet velocity of 0.16 m/ns, which may be used to estimate multi-year sea ice thickness in cases where the ice bottom is detected in ice profile data. |
| Rights: | Approved for public release; distribution is unlimited. |
| URI: | http://hdl.handle.net/11681/9423 |
| Appears in Collections: | CRREL Report |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| CR-85-13.pdf | 4.68 MB | Adobe PDF |  View/Open |