Debris-bed friction of hard-bedded glaciers

摘要: [1] Field measurements of debris-bed friction on a smooth rock tablet at the bed Engabreen, hard-bedded, temperate glacier in northern Norway, indicated that basal ice containing 10% debris by volume exerted local shear traction up to 500 kPa. The corresponding bulk coefficient between dirty and was 0.05 0.08. A model which nonrotating spherical particles are held frictional contact with bed-normal flow can account for these if power law exponent flowing past large clasts is 1. small (n < 2) likely because stresses transient. Numerical calculations drag force sphere flat using n = 1 show this reach values several hundred times isolated from bed, thus drastically increasing resistance. Various estimates obtained model. For example, sliding 20 m a−1 geothermally induced melt rate 0.006 an effective pressure 300 kPa exceed 100 Debris-bed therefore be major component resistance, contradicting common assumption negligible.