Physical modelling of the rheology of clean and sediment-rich polycrystalline ice using a geotechnical centrifuge: potential applications

A self-weight stress gradient is developed through the body of a glacier such that strain rates are highest in the lowest few metres as described by Glen's flow law and other stress- and temperature-dependent relationships. Conventional laboratory technology limits the size and complexity of physical models of glacier ice, particularly in the complicated basal ice layers. A geotechnical centrifuge can be used to replicate such stress regimes in a controlled environment using a scaled model of the field 'prototype' that is subjected to an accelerational field that is a factor N greater than that of the Earth, g. The development of a technique employing a geotechnical centrifuge as a testbed for such physical models is described. Strain rates of 10(-6)-10(-7) s(-1) are calculated for models of low and moderate stress, high temperature ice. Relationships between the physical models and glacial systems suggest a scaling of the effects of transient creep by 1 : N, diffusion creep by 1 : N-2-1 : N-3 and power law creep by 1 : 1. Preliminary results demonstrate the potential applications of the technique in the fields of glaciology and glacial geomorphology, in particular where low stresses and high temperatures are key characteristics of a glacial system and in systems containing several stratigraphic units.