Instability of Large Ice Masses by Finite Element Method

In contrast to the apparently stable behaviour of most ice masses, a small group of glaciers undergo rapid changes in velocity and geometry over a short period of time after having been stable for a large number of years. These periods of fast flow or instability are commonly referred to as surges (Paterson, 1969). Little is known about the mechanical properties, thermal regime and behaviour of such an ice mass prior to and during instability. Although, there appears to be some consensus that surging involves instability at the ice-bedrock interface either due to a positive feedback between water lubrication and basal sliding rate (Weertman, 1969) or a double-valued relationship between basal shear stress and sliding rate at constant normal stress due to cavitation (Lliboutry, 1969).