Researchers from the University of Washington placed fiber-optic cables on the ocean floor near a Greenland glacier and found that collapsing ice creates giant underwater waves, which accelerate melting in ways never measured before.
This technology provides a solution to a dangerous problem in climate research: Scientists need to understand how quickly glaciers disappear, but the front of a glacier, where ice crashes into the sea, is too hazardous for traditional monitoring equipment.
The cable system lets researchers collect vital data from a safe distance.
A University of Washington team dropped a six-mile cable from a boat near a South Greenland glacier. Over the course of three weeks, the cable detected vibrations and temperature changes that uncovered previously hidden processes beneath the ocean surface.
“We took the fiber to a glacier, and we measured this crazy calving multiplier effect that we could never have seen with simpler technology,” said Brad Lipovsky, a University of Washington assistant professor. “It’s the kind of thing we’ve just never been able to quantify before.”
Greenland’s ice sheet contains enough water to lift global sea levels by 25 feet. This frozen mass has been shrinking for 27 years, a development that threatens millions of coastal residents and could disrupt ocean currents that control weather patterns worldwide.
When massive ice chunks break off and slam into the ocean, they create visible tsunami waves. The cables detected a phenomenon researchers had never documented: enormous invisible waves moving between water layers deep below the surface.
“When icebergs break off, they excite all sorts of waves,” explained lead researcher Dominik Gräff.
These hidden waves act like a spoon stirring a drink containing ice. Warm ocean water typically remains below the colder glacier meltwater. However, the underwater waves constantly mix these layers, bringing warm water up to melt the glacier base more quickly than scientists previously understood.
The team watched football stadium-sized ice chunks speed past at up to 20 miles per hour. Major collapses happened every few hours. Each time, building-height waves churned through the fjord long after the surface looked calm, continuously feeding warm water to the glacier.
“Our whole Earth system depends, at least in part, on these ice sheets,” Gräff noted. “It’s a fragile system, and if you disturb it even just a little bit, it could collapse.”
This affordable monitoring method could change glacier research. Fiber-optic sensing costs have plummeted over the past 10 years, making it practical to deploy cables at glaciers worldwide.
The data will help scientists make more accurate predictions about sea-level rise, which will give coastal communities more time to prepare.
Researchers plan to expand this monitoring approach to other threatened glaciers, potentially enhancing early warning systems for hazardous tsunami waves triggered by collapsing ice.
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