Meltwater is thought to be contributing to accelerated glacier flow. Thomas Phillips and his colleagues at the University of Colorado at Boulder show that meltwater seeping through fractures and crevasses in the ice (pictured) can have a sustained warming effect, speeding up ice flow.
By incorporating the effect of this seeping water into thermal models of ice sheets, the authors found that the relatively temperate meltwater warms the surrounding ice, thereby reducing its viscosity and helping to increase its flow. Most of the water refreezes during the winter, but small quantities can remain liquid, causing the sustained warming.
This effect could be leading to much faster glacial responses to warming than current models predict. It is probably contributing to observed changes in some regions of the Greenland ice sheet, the authors suggest.
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Glaciology: Heat trickles down in ice sheets. Nature 468, 8 (2010). https://doi.org/10.1038/468008c