Distributed acoustic sensing (DAS) technology using laser-powered optical-fiber strain sensors can detect subsurface glacial cracks and hidden crevasses down to a depth of 25 meters, according to a published study in Science Advances (doi:10.1126/sciadv.aef1107). Researchers from ETH Zurich verified the method by deploying a single fiber cable alongside micro-electrical-mechanical-system sensor nodes at the Gorner Glacier in the Alps, successfully replacing hundreds of traditional, costly seismographs.
How Distributed Acoustic Sensing Works on Alpine Glaciers
Mountaineers, climate scientists, and polar explorers constantly monitor hidden crevasses that threaten ice stability. Traditional field methods require deploying multiple seismographs across dangerous terrain to record seismic waves generated by fracturing ice, known as icequakes. DAS bypasses these physical hazards by using a single optical fiber to guide a train of laser pulses, as detailed by the ETH Zurich research team.
An interrogator attached to the end of the fiber sends out these pulses and records tiny reflections. Differences in strain along the fiber cause phase changes in the backscattered light. During field tests at the Gorner Glacier—the second-largest glacier in the Alps—ETH researcher Thomas Hudson connected a commercially available DAS platform to a 1-kilometer optical-fiber cable. The cable was slightly embedded into the surface ice during day-night freezing and melting cycles to monitor horizontal acceleration from subsurface movements.
Did you know? During a single week of monitoring at the Gorner Glacier, the DAS grid detected 1,355 distinct “icequakes.” Researchers observed that these seismic events happened with higher frequency when surface temperatures rose above freezing.
Detecting Icequakes to Predict Melting and Calving
Computational analysis of the data collected by the optical-fiber grid allowed the ETH team to map precisely how the glacier fractures beneath its surface. The system identified water- and air-filled gaps that accounted for more than 8 percent of the ice volume within the studied region. According to the researchers, this high-resolution subsurface visualization is critical for understanding structural weaknesses in ice bodies.
The practical applications extend far beyond Alpine research stations. Thomas Hudson stated that the method could help predict changes in polar ice sheets and global sea levels, where ice sheet melting and calving directly impact the world’s oceans. The urgency of these monitoring techniques is underscored by real-world events; as the ETH team finalized their findings in May 2025, a glacial collapse elsewhere in the Swiss Alps destroyed the village of Blatten.
Pro Tip for Field Researchers: Embedding fiber cables into surface ice requires careful timing during natural freeze-thaw cycles. Utilizing a 2D grid layout alongside sensor nodes for vertical acceleration helps cross-verify horizontal strain data captured by DAS channels.
Frequently Asked Questions
What is distributed acoustic sensing (DAS) in glaciology?
DAS is an optical-fiber strain technology that uses laser pulses to measure strain along a continuous cable. In glaciology, it replaces hundreds of individual seismographs to detect subsurface ice fracturing and crevasses.
How deep can optical-fiber sensors detect glacial crevasses?
According to findings published in Science Advances, the ETH Zurich team used DAS to visualize glacial crevasses down to a depth of 25 meters at the Gorner Glacier.
Why are hidden crevasses dangerous for researchers?
Deploying traditional seismographs across unstable ice fields exposes scientists to high risks of falling into hidden subsurface cracks. Optical-fiber cables minimize this danger by covering large areas from a single deployment point.
What triggers an increase in icequakes?
Data from the Gorner Glacier study showed that icequakes occurred more frequently when surface temperatures rose above freezing, driving meltwater movement and structural shifting.
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