Title: The in-situ dielectric constant of polar firn revisited
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 which controls the effective velocity of an electromagnetic wave propagating in an air-ice mixture. An empirical equation for determining the relative real dielectric constant ϵ′r vs. density (specific gravity ϱ) of firn or ice was proposed in 1969 by Robin et al. where ϵ′r = (1 + 0.851 ϱ)2. However, this expression has met with uncertainty because wide-angle radar refraction sounding techniques have produced dielectric constant values that are lower than Robin's equation predicts. This paper discusses radar soundings made on the McMurdo Ice Shelf, Antarctica, and compares the resulting dielectric constant determinations with Robin's equation, laboratory measurements on firn and ice and other expressions given in the literature for determining ϵ′r vs. the specific gravity of dry firn and ice. Our findings indicate that the form of Robin's equation is valid. Our analysis also indicates the expression could be slightly improved to read ϵ′r = (1+0.845ϱ)2. Reasons are suggested as to why previous wide-angle radar sounding studies did not reproduce Robin's findings.
Publication Year: 1995
Publication Date: 1995-05-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 218
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