The Slippery Slope of Ice Sheet Melting

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Melting is traditionally considered a gradual and uniform process — from the Wicked Witch of the West to ice cubes. But what happens when more water is poured on the Witch? Or holes in tops of the ice cubes collapse sending a stream of water right through their centers, while the cubes are simultaneously skidding across the surface of the wet table? For the Greenland ice sheet, the melting and accelerating process of sliding into the sea is giving researchers pause.

Whereas previously lubrication and deep channel flow were seen as an accelerating forces, today, reporting in the journal Nature, Christian Schoof of the University of British Columbia in Canada concludes that large, steady flows through subglacial channels can actually serve to stabilize the overlying ice. The acceleration comes instead, he reports, from short-term spikes in water pressure brought on for example from heavy rains or when surface lakes suddenly drain through the melting ice.

SEE ALSO: Giant Greenland Glacier Cracks Open Overnight

In a separate review of the findings, Swiss glaciologist Martin Lüthi says the process described by Schoof is a “notable advance” on the conventional thinking on the subject.

As Lüthi describes it:

“Surface water is mainly released in pulses — through daily melt, rain or breakthrough drainage from lakes on the ice surface — which are usually shorter than the timescale of channel enlargement. Such brief pressure pulses drive water from channels into the surrounding distributed system, with accelerated sliding being the result.”

SEE ALSO: How Stable Is The West Antarctic Ice Sheet?

IMAGE: A meltwater-filled crevasse, Nature/Christian Schoof

 

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