Large Ice Mass Surging Via Ice-Bedrock Interface Mobilization

A finite element model for surging (instability) of large ice masses is presented. At the interface between the ice and the rock, the basal shear resistance is reduced according to the excess sliding energy dissipated above a certain threshold value. In addition to the threshold energy, the time for surging is also controlled by a lubrication factor. It is confirmed that a geothermal flux approaching 1.9 HFU is required to bring most of the south-west ice-bedrock interface of Barnes Ice Cap (Baffin Island, Canada) to pressure melting which would then allow for basal sliding and instability. It is also shown that the temperature changes during the period of surge of a polythermal ice cap are negligible.