Ice sheet internal radio‐echo reflections and associated physical property changes with depth

Abstract

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 possible means of tracking the internal properties of the ice sheets over large distances. In this paper we use the measured physical properties of core to bedrock taken at Cape Folger, East Antarctica (66°22′S, 111°E, 324‐m depth), to compute a depth‐reflection coefficient profile for comparison with the observed radio‐echo reflections. The measurements available on physical properties are density variations, bubble size and shape changes, and crystal fabric variations. In calculations to differentiate the effects of the physical properties, it appears that density variations account for the primary contributions to the calculated dielectric property changes corresponding to the highest observed reflection coefficients. However, bubble changes alone can also account for reasonable, though lower, reflection coefficients at the depths corresponding to observed reflections. Crystal fabric variations correspond poorly with the reflection locations. The close correspondence between the depths of the bubble shape changes (which are definitely deformational features) and the depths of the density variations, and between both of these and the radio‐echo layers, indicates that deformational events in the ice sheet's history are represented by the variations in physical properties and associated radio‐echo records.