A 2-D numerical model of snow/ice energy balance and ice flow for paleoclimatic interpretation of glacial geomorphic features

Abstract

Standard methods of interpreting the paleoclimates recorded in alpine glacial geomorphic features rely on estimates of paleoglacier shape, commonly assume that relationships between mass balance gradient and equilibrium line altitude of modern glaciers apply equally well to glaciers of, in many cases, dramatically different climates, and do not account for the varying influence of topography on glacial extent. While those methods may be adequate for many studies, there are an increasing number of areas in which that level of analysis does not match the level of detail of the glacial chronologies being developed. As an alternative, we present a physically based, 2-D, glacier model that can be used to determine steady-state glacier shapes and distributions for a wide range of climatic conditions. The model requires only a modest amount of data beyond that which would be required for simpler methods, and includes a relatively accurate representation of the effects of topography on the largest component of the surface energy balance—shortwave radiation. It calculates 2-D, in the horizontal-plane, distribution of snow accumulation using a surface mass and energy balance approach and calculates the resultant glacier shapes with a 2-D flow model. In addition to offering a potentially more accurate reconstruction of paleoclimatic conditions, the model provides a means of performing detailed sensitivity analysis, establishing relationships between similar deposits in basins of different shape and aspect, and of predicting glacier shape terminus position in areas not yet explored.