Dielectric Relaxation in Temperate Glaciers

The dielectric relaxation of névé and glacial ice has been studied on two temperate glaciers in Greenland and France. Measurement of the capacitance and loss tangent in the audio-frequency range of thin parallel wires placed on the surface of a glacier gave ϵ ′, the relative permittivity, and ϵ ″, the loss factor of the névé . The relaxation time can be expressed in terms of the frequency f m at the maximum ϵ ″ value of the Cole-Cole ϵ ″− ϵ ′ diagram, and its variation with depth was derived from the Cole-Cole diagrams obtained for different wire separations. For wet 0°C. surface snow in Greenland, f m ≈ 4 kHz. and decreased with the increase in density and form factor at greater depths, while for the low-density, cold surface névé in France f m ≈ 2 kHz. and increased with the increase in temperature at greater depths. All Cole-Cole diagrams showed both impurity-ion losses at low frequencies below 6 kHz., and a spreading factor of the distribution in relaxation times caused by the changes in the physical properties of the glacier with depth. Although the method could not measure temperatures absolutely, relative temperature differences and the position of the 0°C. isotherm were detected when a temperature gradient existed in a glacier.