Investigating the ratio of basal drag and driving stress in relation to bedrock topography during a melt season on Storglacia¨ren, Sweden, using force-budget analysis

Author： Hedfors Jim Peyaud Vincent Pohjola Veijo A. Jansson Peter Pettersson Rickard

Publisher： International Glaciological Society

ISSN： 1727-5644

Source： Annals of Glaciology, Vol.37, Iss.1, 2003-06, pp. : 263-268

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Abstract

We apply the force-budget technique using the isothermal block-flow model, on Storglaciären, Sweden, to investigate the ratio between basal drag and driving stress in relation to a bedrock ridge in the bed topography during a peak melt season. The input data consist of glacier surface velocities collected using differential global positioning system surveying of a stake net and geometry from previous radar soundings and digitized ice surface maps. The study focuses on the effects of transverse bedrock ridges upon basal stress conditions. The pattern of the calculated ratio of basal drag and driving stress shows a rhythmical position of relatively high and low basal drags on the stoss and lee sides, respectively, of the bedrock thresholds. One of the zones of low basal drag corresponds to the location where the highest basal sliding rate has been measured previously by borehode deformation studies. This zone also aligns with the area where the drainage system is suggested to change from englacial to subglacial.