Tiny Sand Grains Trigger Massive Glacial Surges – Suddenly Spilling Over the Land at 10 to 100 Times Their Normal Speed

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Tiny Sand Grains Trigger Massive Glacial Surges – Suddenly Spilling Over the Land at 10 to 100 Times Their Normal Speed

A surging glacier in the St. Elias Mountains, Canada.

 

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New model answers longstanding question of how these sudden flows happen; may expand understanding of Antarctic ice sheets.

 

About 10 percent of the Earth’s land mass is covered in glaciers, most of which slip slowly across the land over years, carving fjords and trailing rivers in their wake. But about 1

 

percent of glaciers can suddenly surge, spilling over the land at 10 to 100 times their normal speed. 

 

When this happens, a glacial surge can set off avalanches, flood rivers and lakes, and overwhelm downstream settlements. What triggers the surges themselves has been a

 

longstanding question in the field of glaciology. 

 

Now scientists at MIT and Dartmouth College have developed a model that pins down the conditions that would trigger a glacier to surge. Through their model, the researchers

 

find that glacial surge is driven by the conditions of the underlying sediment, and specifically by the tiny grains of sediment that lie beneath a towering glacier.

 

“There’s a huge separation of scales: Glaciers are these massive things, and it turns out that their flow, this incredible amount of momentum, is somehow driven by grains of

 

millimeter-scale sediment,” says Brent Minchew, the Cecil and Ida Green Assistant Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “That’s a hard

 

thing to get your head around. And it’s exciting to open up this whole new line of inquiry that nobody had really considered before.”

 

The new model of glacial surge may also help scientists better understand the behavior of larger masses of moving ice. 

 

“We think of glacial surges as natural laboratories,” Minchew says. “Because they’re this extreme, transient event, glacial surges give us this window into how other systems work,

 

such as the fast-flowing streams in Antarctica, which are the things that matter for sea-level rise.”