On the nature, interpretation, and application of electromagnetic reflections in cold ice

Abstract

The investigation of glaciers and ice sheets by means of ice penetrating radar has become one of the most commonly used geophysical techniques in glaciology.This doctoral thesis contributes new approaches and results to the analysis of electromagnetic reflections originating within cold ice bodies.Main subject is the direct comparison of synthetic radargrams with radar survey data and the explanation of results thereof, especially in view of climatic interpretation of ice core records.In addition, new evaluations of survey techniques and data analyses are presented.Focusing on the region surrounding the EPICA ice core deep drilling location in Dronning Maud Land, Antarctica, different numerical forward modeling techniques are used. Physical in-situ properties are taken from three shallow ice cores for which profiles of the complex dielectric constant are available, radar reference traces are determined from surface-based radar surveys.Application of combined ice core and radar analyses focus on internal reflection horizons.The successful forward modeling allows numerical sensitivity studies with altered dielectric ice core data. Findings confirm earlier assumptions that changes in permittivity are responsible for observed reflection horizons in the upper part of the ice sheet.Although variations in conductivity are negligible for causing reflections, strong correlations of permittivity and conductivity signals indicate a mutual influence, and validate the isochronous character of reflection horizons.Based on this property, the error involved in the dating of reflection horizons and synchronization of ice cores is evaluated for the ice sheet in Dronning Maud Land and additionally for the cold alpine saddle Colle Gnifetti (Monte Rosa, Valaisian Alps).The results are promising as the errors determined in both studies are only relatively larger than the initial uncertainty related to ice core dating.