A theory of glacier surges

摘要: We propose a model of glacier flow that is capable explaining temperate surges. The laws conservation mass and momentum are supplemented by the prescription sliding law gives basal shear stress τ as function velocity u effective pressure N. drainage N determined simple study subglacial hydraulic system. Following Rothlisberger, we determine = NR for case through single tunnel. Alternatively, following Kamb, find corresponding theory linked-cavity system yields NK < NR. Furthermore, stability each depends on u, such large enough there transition from tunnel to cavity drainage. Consequently, one can write N(u). then τ(u) multivalued, hence so also flux/depth relation Q Q(H). An analysis resulting equations sketched. For accumulation rates, will undergo regular relaxation oscillations, resembling surge. surge triggered at point maximum stress; this two fronts travel up down calculable boundary points. speed propagation order 50 metres an hour. At these fronts, collapses, high water installed. This activated zone has velocities quickly relaxes (surges) quasi-equilibrium state. much like opening sluice gate, in wave front propagates forward. Behind front, decay oscillatorily, thus be compressive. conclude with some discussion effects seasonal variation prospects current theory's applicability soft-bedded glaciers.