Variations in Hard-Bedded Topography Beneath Glaciers

Abstract:

The morphology of the beds of glaciers is a first order control on their sliding speeds and consequent rates of subglacial erosion. As such, it is important to constrain the range of bed shapes expected beneath glaciers. To estimate the variability of subglacial bed morphology, we constructed ten high resolution (10 cm) digital elevation models of recently exposed proglacial areas from point clouds produced through a combination of terrestrial laser scanning and structure-from-motion techniques. The proglacial areas are located in the Swiss Alps and the Canadian Rockies and consist of predominantly debris-free bedrock of variable lithology (igneous, sedimentary, and metamorphic). We measured eight different spatial parameters intended to describe obstacle shapes generated beneath glaciers. Using principal component analysis and Bayesian statistical models to investigate the significance of these spatial parameters, we find that most of the studied proglacial areas have a high level of morphological similarity. Within individual proglacial areas, areal distributions of morphological parameters are largely self-similar with only a small number of morphologically distinct sections. The uniformity of bed morphologies between proglacial areas indicates that the effects of glacier slip and erosion acting on hard beds may cause most beds to trend towards a relatively limited range of morphologies.