Lately I have been reading articles in Science News and elsewhere about glacial lakes melting holes through very thick glaciers and disappearing through said holes. It appears that this additional water further lubricates the interface between the ice and the rock below, increasing the rate of glacier flow.

Since ice floats in water, a water lake on top of a glacier is metastable and really wants to be under the glacier. The question is, how does it get there without freezing over?

As you know, around the ice/water phase transition a pressure increase can induce melting (due to the lower specific volume of water). Thus, if the lake is deep enough, hydrostatic pressure at the boundary may be large enough to induce melting. The open boundary of the lake will probably undergo some freezing, but once frozen over the ice layer acts as a thermal insulator and this process slows down. The pressure melting of ice at the bottom is a runaway process.


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