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January 18th, 2008

Alaska glacier speed-up tied to internal plumbing

Masters student Tim Bartholomaus with Bob and Suzanne Anderson have published their work on the sliding of Alaska's Kennicott Glacier as the cover article in the 1st issue of new journal Nature Geoscience. Their results show meltwater periodically overwhelms the interior drainpipes of the glacier and causes it to lurch forward, similar to processes that may help explain the acceleration of glaciers observed recently on the Greenland ice sheet that are contributing to global sea rise.

Detailed measurement of glacier speed using 5 GPS monuments, water depths in side-glacier lake basins, and water discharge in the outlet river, strongly argue that basal motion (sliding and/or till deformation) occurs whenever water inputs into the glacier exceed the capacity of the glacial plumbing system to transmit the water. Excess water backs up into the distributed cavity system at the glacier bed, increasing the pressures that promote sliding. This overcharging of the plumbing system occurs during diurnal melt cycles, seasonal cycles, and during the huge annual outburst flood that runs a natural hydrology experiment on the glacier each summer.

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