Relaxation Self-Oscillations and Processes at the Bottom of Glaciers

Abstract

In terms of the theory of oscillations, rapid glacier advances (glacier surges) are relaxation self-oscillation, and large glacier advances of the same character dependent on climate are the result of interaction between forced and self-exciting oscillations.

The relation is found between average shear stress and sliding velocity of pure and of moraine-containing ice along the bottom, taking into account the real thermal and kinematic boundary conditions, the different dependence of the ice melting point on hydrostatic pressure

and on normal component of the stress deviator, and dry friction against the bottom. In the regime of bottom melting, a communicating system of subglacial drainage channels is formed along (he borders of distal slopes of bottom irregularities. Variations of effective roughness lead to the forced variations of sliding velocity depending on the surface melting rate.

Relaxation self-oscillations of glaciers are caused by the alternation of “sticking” to the bottom in the phase of restoration and of rapid sliding along the bottom in the phase of relaxation because of the changes in the concentration of moraine material in the bottom layer of ice and of the force of dry friction against the bottom of a glacier.