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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
Marine geophysics
Sea ice
Sea ice measurement
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.
Appears in Collections:CRREL Report

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