The Low Frequency Electrical Properties of Sea Ice
This thesis summarises an experimental and theoretical study of the low frequency electrical properties of sea ice. The aim of the research was to first demonstrate, and then gain a physical understanding of, the microstructural dependence of a sea ice impedance measurement. In particular, we sought to realise how the effective electrical properties of the medium depended on the volume fraction, orientation, dimensions, and connectivity of the dispersed brine phase. The experimental portion of the project was performed on laboratory grown, artificial sea ice. We monitored the variation with time, and temperature, of the broadband sea ice impedance using four-electrode measurement cells embedded within the ice. The four-electrode measurement allowed us to realise and eliminate the contribution of electrode polarization to the measured impedance. By representing the electrical response of sea ice as a complex conductivity, we formulated a broadband physical model to describe the medium. The model distinguished bulk conduction, bulk polarization, and interfacial polarization. A complex non-linear least squares fitting procedure revealed the individual contribution of these physical processes and we studied their variation with temperature. We found that the bulk material underwent a dielectric relaxation with activation energy Ea = 0.20 + and - 0.04eV. We linked the bulk material properties with a two phase microstructural model, with realistic input parameters.