Bernard Hallet

Glacial Abrasion and Sliding: their Dependence on the Debris Concentration in Basal Ice

A model of bedrock abrasion by a temperate glacier is developed that takes into account the significant impeding effect of scattered rock fragments at the ice-rock interface on glacier sliding. An increase in the debris concentration above a relatively low value can reduce the abrasion rate by decreasing both the flux of rock fragments and the effective forces which press fragments against the bed. Abrasion of a simple wavy bed is shown to be most rapid for a relatively low debris concentration above which the abrasion varies inversely with the debris content. A similar concentration dependence of abrasion is expected for beds of arbitrary geometry but low roughness. Sliding glaciers will tend to abrade until the basal ice is nearly stagnant at which point rocks of all sizes start to lodge against the bed.