Structural Studies of Subpolar Glacier Ice

Abstract

Structural studies including orientation of respectively bubbles, foliation plane and englacial moraine particles as well as ice fabric studies have been carried out on subpolar glacier ice from the Kebnekaise region in northern Swedish Lapland. Most of the work was done in a cold laboratory, work on the glacier itself was restricted to achieve complementary information such as velocity and direction of ice movement and strain-rate measurements.

The ice crystals, which were taken from the snout of Isfallsglaciären, were very large. One crystal was found to be at least 26 cm long. No difference in crystal size could be detected in the uppermost 15 m in this part of the glacier. Although the ice crystals are complexly shaped a definite dimensional orientation has been found.

The ice fabrics also display a very anisotropic pattern consisting of six point maxima at constant angular distances from each other. The pattern is independent of the structural type of ice present, but seems to fit a combination of Kamb's theory of crystal orientation in a general stress field and Brace's corresponding theory for a uniaxial stress field.