Call number:
ZSP-201-78/4
In:
CRREL Report, 78-4
Description / Table of Contents:
The use of radio-echo sounding records to indicate the presence of internal layers within large ice sheets is of interest to glaciologists because it offers a means of tracking the internal properties of the ice sheets over large distances. The interpretation of the reflections obtained in this manner is more valuable, however, if a physical property change relating to the glaciological regime can be related to the dielectric property change producing the radio-echo reflections. In this report, we use the measured physical properties of core to bedrock taken at Cape Folger, East Antarctica (66 deg 22 min s, 111 deg (E), 324-m depth), to compute a profile of dielectric properties and from this, a depth-reflection coefficient profile for comparison with observed radio-echo reflections. The measurements available on physical properties are: density variations, bubble size and shape changes, and crystal fabric variations. The depths of the strong reflections shown on the available radio-echo records are in reasonable agreement with the depths corresponding to the highest reflection coefficients computed from the combined physical property measurements. In calculations to differentiate the separate effects of different physical properties, it appears that density variations account for the primary contributions to the calculated dielectric property changes corresponding to the highest reflection coefficients. However, bubble changes alone can also account for reasonable, though lower, reflection coefficients at the appropriate depths. Crystal fabric variations correspond poorly with the reflection locations. Density variations are normally associated with depositional events in the history of the ice sheet.
Type of Medium:
Series available for loan
Pages:
vi, 12 Seiten
,
Illustrationen
Series Statement:
CRREL Report 78-4
URL:
https://hdl.handle.net/11681/9416
Language:
English
Note:
CONTENTS
Abstract
Preface
Nomenclature
Introduction
Derivation of the power reflection coefficient-depth variation
Possible sources of dielectric constant variation with depth in ice sheets
Ice density variations
Effect of macroscopic impurity layers
Effect of microscopic impurtty layers
Changes in inclusion geometry
Effect of crystal orientation changes
Physical properties of the Cape Folger core
Density-depth profile
Air bubble-geometry depth profile
Crystal orientation-depth profile
Radio-echo sounding data
Results and conclusions
Literature cited
Location:
AWI Archive
Branch Library:
AWI Library
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