New ways of studying ice sheet flow directions and glacial erosion by computer modelling—examples from Fennoscandia

Abstract

A computer ice sheet model has been used to study regional ice flow directions and glacial erosion of the Weichselian ice sheet, adopting a new method of presenting modelled ice flow directions. Ice sheet model results from different time periods during the Weichselian were extracted for five regions and presented in rose diagrams. When comparing these computer-generated results with information on flow directions obtained from current conceptual geological models based on field data, large similarities were observed. In comparing the ice flow directions as such, the similarities were strikingly good. In many cases there was also a good agreement in the timing of the events, while in some cases a certain flow direction was assigned to a different time period by the ice sheet model than in the current interpretation of geological information. Nevertheless, the overall agreement between the data sets shows that results from ice sheet models can aid in placing geological information into a coarse timeframe and chronostratigraphic context, and also fill in time gaps in the glacial geological record where chronological control is sparse. Ice sheet model results thus constitute a new data set against which glacial geological information can be compared and tested. A new quantity, basal sliding distance, has also been calculated from the ice sheet model results, describing the over time accumulated length of ice that has passed over the landscape by basal sliding. The results show high basal sliding distance values in SW Sweden/SE Norway, in Skagerrak, and along the Gulf of Bothnia, implying relatively large amounts of glacial erosion in these regions. On elevated parts of the Scandinavian mountain range and on adjacent plains in the east the basal sliding distance values are low, implying weaker glacial erosion. This compares well with different types of geological and morphological data, suggesting that basal sliding distance is a useful entity for studying regional patterns of glacial erosion intensity.