Researchers have discovered that massive hidden underwater waves, triggered by iceberg calving, significantly intensify the melting of Greenland's glaciers. Using a 10-kilometer fiber-optic cable, an international team measured these waves for the first time. The findings reveal a powerful mixing effect that brings warm seawater into contact with glacier bases, accelerating ice loss.
An international team led by the University of Zurich and the University of Washington has uncovered how iceberg calving generates hidden underwater waves that supercharge glacier melting in Greenland. The research, part of the GreenFjord project supported by the Swiss Polar Institute, focused on the Eqalorutsit Kangilliit Sermiat glacier in southern Greenland, which releases about 3.6 cubic kilometers of ice into the ocean each year—nearly three times the annual volume of Switzerland's Rhône glacier.
During an extensive field campaign, scientists deployed a 10-kilometer-long fiber-optic cable on the seafloor across the fjord in front of the glacier. Employing Distributed Acoustic Sensing (DAS), the cable detected tiny vibrations from events like falling ice blocks and ocean waves. "This enables us to measure the many different types of waves that are generated after icebergs break off," says lead author Dominik Gräff, a University of Washington postdoctoral researcher affiliated with ETH Zurich.
When icebergs calve and crash into the water, they create surface tsunamis that mix upper water layers. More crucially, internal underwater waves—reaching heights comparable to skyscrapers—persist between density layers, continuously bringing warmer, denser seawater upward. This enhances melt erosion at the glacier's base. "The warmer water increases seawater-induced melt erosion and eats away at the base of the vertical wall of ice at the glacier's edge. This, in turn, amplifies glacier calving and the associated mass loss from ice sheets," explains Andreas Vieli, a professor in the University of Zurich's Department of Geography.
"The fiber-optic cable allowed us to measure this incredible calving multiplier effect, which wasn't possible before," adds Gräff. The Greenland ice sheet, covering an area 40 times larger than Switzerland, could raise global sea levels by seven meters if fully melted. Such retreat also disrupts ocean currents like the Gulf Stream and affects fjord ecosystems. "Our entire Earth system depends, at least in part, on these ice sheets. It's a fragile system that could collapse if temperatures rise too high," warns Gräff.
The study was published in Nature on November 13, 2025.