Glacial plumbing

The water on top of glaciers will frequently melt and form large lakes when exposed to sunlight for sustained periods during the summer months. Now it appears that this melt-water can tunnel down through glaciers up to a kilometer thick, in a process called hydrofracture, with alarming implications for the entire system.

If a tunnel of melt-water moves water all the way down to the base of the glacier, it will lubricate the movement of the ice sheet, allowing it to speed up its flow. If this acceleration is localised, the possibility exists of more crevasses opening up. More melt-water flows to the base of the glacier and so on… At the same time, the glacier experiences an upthrust from the volume of water flowing under it.

In Greenland a meltwater lake covering 5.6square kilometers was observed to drain to the bottom of a glacier in one 24 hour period.

Whether movements on this scale are a natural phenomenon or the result of human  activity driving global warming is the subject of ongoing debate.

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