In a groundbreaking study unveiled this August, scientists deployed a novel fiber-optic sensing technology beneath the icy waters of South Greenland’s fjords to capture, in unprecedented detail, the dynamic processes of glacier calving — the dramatic fracturing and disintegration of ice sheets that significantly drive sea level rise and alter oceanic systems. This innovative approach, harnessing Distributed Acoustic Sensing (DAS) on a 10-kilometer submarine fiber-optic cable, offers a transformative window into the intricate interplay between melting ice and seawater, overcoming the extreme hazards that have long hindered direct observation of these colossal natural events.
Glaciers, immense reservoirs of frozen freshwater, are crucial regulators of Earth’s climate. Their catastrophic disintegration, known as calving, involves massive ice chunks breaking free and plunging into the sea with tremendous force, creating tsunamis and ripples that propagate throughout the fjord. Traditional data collection methods, constrained by the inaccessibility and danger of glacier fronts, have offered only fragmented or indirect glimpses of these processes. The integration of fiber-optic cables equipped with DAS technology circumvents these challenges by transforming the cable itself into a dense array of seismic and acoustic sensors that register even the minutest ground and water movements, effectively translating the natural “language” of vibrations into a rich dataset.
Led by researchers from the University of Washington, the team orchestrated a field deployment near the Eqalorutsit Kangilliit Sermiat glacier, threading a fiber-optic cable along the seafloor directly in front of the glacier terminus. Over three weeks, the array continuously recorded high-resolution ground motion and temperature variations, capturing the subtle nuances and enormous energy bursts associated with calving events. This approach allowed scientists to monitor ice chunks the size of football stadiums hurtling through the fjord at speeds approaching twenty miles per hour, and to measure the resultant waves shaping the local hydrodynamics.
Beyond the dramatic surface impacts, the study revealed an intricate hierarchy of underwater wave phenomena generated by the calving ice. Initial splashes produced massive surface waves akin to localized tsunamis, which agitated the upper layers of the fjord’s stratified water column. More intriguingly, the submerged fiber sensing detected internal gravity waves—immense, stealthy oscillations propagating between layers of varying water density. These waves, invisible from above, rock the entire water column, dramatically enhancing mixing processes and accelerating the melting dynamics beneath the glacier face by disrupting the thermally insulating layers.
The physical analogy employed by the researchers compares this underwater agitation to stirring ice cubes in a warm beverage: without stirring, a cold boundary layer forms around the cubes, slowing melting; with vigorous mixing, the insulating layer is disrupted, and melting accelerates. In the fjord’s context, calving-induced wave activity serves as this “stirring” mechanism, potentially amplifying the rate at which submerged glacier ice dissolves into the ocean. These insights constitute a significant leap forward in understanding the feedback mechanisms that exacerbate glacial retreat and contribute to accelerating sea-level rise.
This pioneering use of DAS on submarine cables represents a revolution in glaciological observation. Unlike conventional methods that rely on stationary ocean-bottom seismometers or vertical temperature probes—both offering limited spatial and temporal snapshots—the fiber-optic system provides continuous, spatially distributed sensing across kilometers of the marine environment. This holistic view uncovers previously unseen processes, such as the sustained influence of internal waves and their role in modulating thermal exchange and water circulation beneath the glacier.
Furthermore, the high-resolution temporal data acquired enabled detailed quantification of frequency and intensity of calving events, recorded roughly every few hours during the field campaign. This level of continuous observation is crucial to refine numerical models predicting glacier behavior and downstream impacts on global ocean circulation. The Greenland ice sheet, which blankets an area three times the size of Texas, is a pivotal climate player; its accelerating mass loss poses an existential threat by raising sea levels up to 25 feet, potentially drowning coastal cities worldwide and reshaping human societies.
Moreover, this research underscores the cascading impacts of glacial dynamics on the broader Earth system. The Greenland ice sheet interacts intimately with the Atlantic meridional overturning circulation (AMOC), a critical conveyor of heat and nutrients connecting northern and southern ocean basins. Disruptions to this circulation due to accelerated ice melt could destabilize global climate patterns, altering weather extremes and marine ecosystems. Precise sensing technologies like DAS serve as essential tools to monitor these changes in real time, offering the potential to enhance early warning systems for calving-induced tsunamis and other hazards.
The multidisciplinary collaboration that made this study possible combined experts from Earth and space sciences, oceanography, engineering, and geophysics, spanning institutions across the United States and Europe. By integrating insights from field observations with advanced sensing and modeling techniques, the team not only pushed technological boundaries but also deepened fundamental understanding of glacier-ocean interactions, providing critical knowledge needed for climate adaptation and mitigation strategies.
As fiber-optic sensing continues to evolve and become more accessible, its applications are rapidly expanding beyond conventional domains, from urban seismology to deep-sea monitoring. This project exemplifies its transformative potential in remote, harsh environments where traditional instrumentation struggles. The success of applying DAS in monitoring Greenland’s calving dynamics opens avenues for similar deployments around the world’s ice sheets and coastal glaciers, enabling scientists to capture the fine-scale processes driving global sea-level changes with unparalleled fidelity.
In light of accelerating climate change, such advancements arrive just in time. As Earth’s polar ice margins retreat with increasing speed and unpredictability, continuous, high-resolution data streams are indispensable for validating climate models, guiding policy decisions, and protecting vulnerable populations. The fiber-optic technique not only heralds a new era of glaciological research but also marks a critical step towards comprehensively understanding and responding to the cascading effects of ice loss in an interconnected global system.
For inquiries and further information on this pioneering research, contact lead researcher Dominik Gräff at graeffd@uw.edu.
Subject of Research: Glacier calving dynamics and fjord hydrodynamics using fiber-optic distributed acoustic sensing.
Article Title: Calving-driven fjord dynamics resolved by seafloor fibre sensing
News Publication Date: 13-Aug-2025
Web References:
- Nature article: http://dx.doi.org/10.1038/s41586-025-09347-7
- Related research on Atlantic meridional overturning circulation: https://pmc.ncbi.nlm.nih.gov/articles/PMC11578178/
- NOAA Arctic Report Card on Greenland ice sheet: https://arctic.noaa.gov/report-card/report-card-2024/greenland-ice-sheet-2024/
References:
Calving-driven fjord dynamics resolved by seafloor fibre sensing, Nature, 2025. DOI: 10.1038/s41586-025-09347-7
Image Credits: Manuela Köpfli / University of Washington
Keywords: Glacier calving, fiber-optic sensing, distributed acoustic sensing, fjord dynamics, Greenland ice sheet, sea-level rise, internal gravity waves, ocean circulation, climate change, glacial melt, seafloor cable, cryosphere monitoring
