Recrystallisation and electrical behaviour of glacier ice

Electrical d.c. resistivity measurements made on the George VI Ice Shelf have established the polar nature of Antarctic ice despite saturation by melt-water from surface melt-lakes. Previously it has been suggested that different impurity concentrations are responsible for the extremes in resistivity (a factor of 1,000) between temperate ice (essentially at its pressure melting point) and polar ice (well below its pressure melting point). However, the evidence suggests that impurity levels are similar despite the leaching of contaminants by free water in temperate glaciers, a process which is absent in true polar glaciers. This implies that, although impurities can significantly alter the electrical behaviour of glacier ice, there is a more fundamental mechanism at work. We suggest that this process is one of recrystallisation