ABSTRACT: Numerical modeling of the development of U-shaped valleys by glacial erosion

CGRG Bibliography of Canadian Geomorphology
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Abstract

It is possible to investigate the development of U-shaped valleys by linking a finite-element model for ice flow through a glacier cross-section with an erosion model. To simulate valley development, the flow through an initial glacier cross-section is modeled and the glaciological parameters that govern erosion are calculated. Then erosion is numerically simulated to produce a modified transverse profile, for which a new flow field and erosion pattern are computed. A number of iterations permits examination of the progressive transformation of cross-section form, which can be compared with field data. Model predictions of the cross-section flow field were in close accord with data from the Athabasca Glacier (Alberta, Canada), including marked lateral variations in sliding velocity. With an erosion law dependent on basal velocity, the model predicted the rapid transformation of a V-shaped cross-section intoa recognizably glacial form over a time period on the order of 10,000 years and the eventual development of a steady-state, quasi-parabolic glacier cross-section. Better agreement with empirical data from glaciated valleys was obtained by including temporal variations in ice discharge, in order to mimic the characteristics of 100,000-yr glacial cycles. The high-discharge phase dominated form development, and, at low discharges, cross-section form was essentially inherited from the central part of the form that developed during the preceding high-discharge phase. A major limitation of the current model is that it cannot address the complications that arise from the fact that glacier cross-sections are not isolated entities, but part of three-dimensional systems; the problem of glacial-valley development would best be addressed using a three-dimensional model of glacier flow to examine the interactions between long-profile and cross-profile development

Bibliography of Canadian Geomorphology