The kinematic significance of subglacial bedforms and their use in palaeo-glaciological reconstructions

Abstract

Subglacial bedforms are relevant geomorphic markers for palaeo-glaciological reconstructions. Due to the complexity of thermomechanical interactions between ice, till and water on subglacial beds, their formation processes and significance in palaeo-glaciology are still controversial. Based on the measurement and comparison of morphometric characteristics (length, width, amplitude, area and volume) of ∼250 000 bedforms formed below terrestrial ice sheets during the last glacial period, we propose a unified kinematic model, consistent with the ‘bed deformation model’, whereby bedform shapes and orientations depend on their degree of evolution and reflect the magnitude and orientation of finite bed deformation in response to motion of the overlying ice. Two application examples from the Low Land Ice Dome (British-Irish Ice Sheet) and Keewatin Ice Dome (Laurentide Ice Sheet) demonstrate how this model enables the derivation of palaeo-glaciological maps of finite bed deformation, which can then be used to better constrain ice flow directions, their relative velocities, and the location of subglacial drainage routes.