Interfacial water in polar glaciers and glacier sliding at -17 degrees C

We have observed sliding at a cold (-17 degrees C) ice-rock interface benea th Meserve Glacier, Antarctica, and the segregation of ice into clean lense s amidst the dirty basal layers of this glacier. We interpret these as mani festations of thin water films at ice-rock interfaces. We use Shreve's theo ry for sub-freezing sliding to estimate the nominal film thickness to be at least tens of nanometers. Such water films should exist around rocks in mo st polar ices, and likely have high solute concentrations due to solute rej ection during regelation and due to exchange with veins and grain boundarie s where impurities reside.