Monitoring the temperature-dependent elastic and anelastic properties in isotropic polycrystalline ice using resonant ultrasound spectroscopy

Matthew J. Vaughan,David J. Prior,M. Hamish Bowman,Kasper van Wijk

doi:10.5194/tc-10-2821-2016

Abstract

Abstract. The elastic and anelastic properties of ice are of interest in the study of the dynamics of sea ice, glaciers, and ice sheets. Resonant ultrasound spectroscopy allows quantitative estimates of these properties and aids calibration of active and passive seismic data gathered in the field. The elastic properties and anelastic quality factor Q in laboratory-manufactured polycrystalline isotropic ice cores decrease (reversibly) with increasing temperature, but compressional-wave speed and attenuation prove most sensitive to temperature, indicative of pre-melting of the ice. This method of resonant ultrasound spectroscopy can be deployed in the field, for those situations where shipping samples is difficult (e.g. remote locations), or where the properties of ice change rapidly after extraction (e.g. in the case of sea ice).

Highlights

Ice sheets flow due to a combination of internal deformation and sliding at the base of the ice
The rate of internal deformation is strongly dependent on the englacial temperature, with flow rates increasing for warmer ice
Englacial and basal temperatures across the vast majority of the Antarctic and Greenland ice sheets are subject to uncertainties on the order of several degrees Celsius, limiting our ability to accurately model the contributions of internal deformation and basal sliding to ice-sheet flow

Summary

Introduction

Ice sheets flow due to a combination of internal deformation and sliding at the base of the ice. An englacial temperature uncertainty of 5 ◦C corresponds to an uncertainty in internal deformation rates of a factor of 2 to 5 (using activation enthalpies for ice sheets; Cuffey and Paterson, 2010). For frozen base scenarios (such as parts of Antarctica), the uncertainties on basal sliding rates that correspond to uncertainty on basal temperature will be of the same order of magnitude. Englacial and basal temperatures across the vast majority of the Antarctic and Greenland ice sheets are subject to uncertainties on the order of several degrees Celsius, limiting our ability to accurately model the contributions of internal deformation and basal sliding to ice-sheet flow. Geophysical methods (ice-penetrating radar and active-source seismology) can provide data on internal structure and physical properties of ice

Results

Discussion

Conclusion