Abstract:
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.
