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4. CRREL Report

Title:	A reassessment of the in-situ dielectric constant of polar firn
Authors:	National Science Foundation (U.S.). Division of Polar Programs. Kovacs, Austin. Gow, A. J. (Anthony Jack) Morey, Rexford M.
Keywords:	Antarctica Firn Ice shelves Dielectric constant Glacial sounding Radio echo sounding Radio wave propagation Glaciology EPOLAR
Publisher:	Cold Regions Research and Engineering Laboratory (U.S.) Engineer Research and Development Center (U.S.)
Series/Report no.:	CRREL report ; 93-26.
Description:	CRREL Report Abstract: The success in using VHF and UHF frequency systems for sounding polar ice sheets has been tempered by an uncertainty in the in-situ dielectric constant ε', which controls the effective velocity Ve of an electromagnetic wave propagating in an air-ice mixture. An empirical equation for determining ε' vs. density (specific gravity, ρ) was proposed in 1968 by Robin et al. where ε'= (1 + 0.851 ρ)^2. However, this expression has met with uncertainty because wide-angle radar refraction sounding techniques have produced values of ε' that are lower than Robin's equation predicts. This report discusses radar soundings made on the McMurdo Ice Shelf, Antarctica, and compares the resulting ε' values with Robin's equation, laboratory measurements on firn and ice and other expressions given in the literature for determining ε' vs. the specific gravity of dry firn and ice. Our findings indicate that the form of Robin's equation is valid. However, our analysis also indicates the expression could be slightly improved to read ε' = (1 + 0.845 ρ)^2. Reasons are suggested as to why previous wide-angle radar sounding studies did not reproduce Robin's findings.
Rights:	Approved for public release; distribution is unlimited.
URI:	http://hdl.handle.net/11681/9176
Appears in Collections:	CRREL Report