Reconstructing the evolutionary dynamics of former ice sheets using multi-temporal evidence, remote sensing and GIS

Abstract

Recent advances have been made in the way in which former ice sheets are reconstructed from the fragmentary geomorphological and geological evidence that they leave behind. The use of satellite images to view large scale glacial geomorphology has revealed cross-cutting patterns that record changing flow configurations through time. These flow changes may arise from migrating ice divides, the switching on and off of ice streams, margin retreat or flow patterns from more than one glaciation. Such multi-temporal evidence permits more detailed reconstruction of the evolution of former ice sheets which contrasts with previous reconstructions of just glacial maxima or deglacial retreat. Increased complexity of ice flow and the realisation that evidence may relate to different time-slices of ice sheet history have led to the use of geographical information systems (GIS) to integrate a wide variety of different lines of evidence, to permit the construction of ice dynamic scenarios. The use of remote sensing and GIS for palaeoglaciological reconstruction is reviewed, and its impact assessed. Recommendations for processing of remotely sensed data (optical and radar) for use in glacial geomorphological mapping are outlined. An overall reconstruction strategy which uses remote sensing to acquire ice flow information and a GIS to integrate it with field evidence is suggested. Reconstructions based on geological and geomorphological evidence are now capable of providing rigorous tests for ice sheet modelling experiments. It is anticipated that future links between modelling and ice sheet wide reconstructions will yield major advances in our understanding of both the physics of ice sheets and the behaviour of former ice sheets.