Research

Distributed fiber sensing measures changes in light as it travels through an optical cable, transforming the cable into a dense array of sensors. Distributed Acoustic Sensing (DAS) records seismic and acoustic strain or strain rate; Distributed Temperature Sensing (DTS) resolves temperature. Measurements can be made every few meters along cables extending roughly 100–150 kilometers—and much farther when existing telecommunications systems can be used [34].

A foundational question is deceptively simple: what does a fiber actually measure? Through field experiments, laboratory calibration, theory, and comparisons with broadband seismometers, the group has helped establish when DAS can be interpreted as a dense array of one-component strain seismometers [28]. These observations turn natural and engineered systems into direct tests of how deformation localizes, friction evolves, fractures propagate, and waves carry information about failure. Recordings of earthquakes, ocean waves, ships, and marine-mammal vocalizations also test the technology’s bandwidth and reveal how acoustic and seismic waves propagate through water, sediment, rock, and ice [20, 22, 37].

The group also works on the practical barriers created by instruments that can generate terabytes of data per day. Collaborative research on data storage, compression, reconstruction, wavefield separation, and edge computing makes large fiber datasets usable without discarding their essential physics [23, 26].

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Glaciers and ice sheets are natural laboratories for fracture, friction, deformation, and failure across scales. Their evolution is governed by processes at boundaries—where ice meets ocean, rock, water, and atmosphere. The group combines fiber sensing, seismology, remote sensing, glacier-flow models, and fracture mechanics to connect fast local processes with the large-scale evolution of ice.

Calving fronts and ice–ocean interaction

Seafloor fiber observations in Greenland showed that iceberg calving generates internal waves and fjord circulation that enhance submarine melting. The Nature study, led by postdoctoral scholar Dominik Gräff, revealed calving as an active driver of ocean mixing rather than only a response to ocean forcing. This coupling offers a mechanism that may help explain why models underestimate frontal ice loss [31].

At the global scale, work led by former student Simon-Hans Edasi showed that water-terminating glaciers are systematically thicker than land-terminating glaciers. The result links marine ice-cliff physics to glacier geometry and shows that processes associated with instability can also help set a stable mean state [35].

Ancient ice and climate archives

At the other end of the dynamical spectrum, the group studies how ice millions of years old can survive in the Allan Hills of Antarctica. Microstructural observations of ice fabric, texture, and bubbles reveal deformation that can complicate interpretation of these climate archives [38]. Complementary work led by John-Morgan Manos links ice flow, thermodynamics, and boundary interactions to identify pathways that preserve ancient ice. That framework predicts where ice more than ten million years old may occur, providing a prospecting tool for climate records far older than conventional ice cores.

Ice-shelf rifts are the largest fractures in glacier systems. Brad described the largest glacier fracture event yet recorded and showed that coupling to the ocean limits its rupture velocity. That observation demonstrates that the surrounding fluid can control fracture propagation—not only the mechanics of the ice itself [24].

This work builds on studies of the ways tides, ocean swell, temperature, geometry, and stress state trigger and regulate rift growth [6, 11, 14, 18]. Mechanics-based models explain when rifts remain stable, when they propagate, and how fracture, flexure, viscous ice flow, and surface meltwater interact [13, 32]. Work on engineered hydraulic fractures provides a complementary setting in which theory can be tested against controlled forcing, while connecting glacier failure to fluid-driven fracture in volcanoes, geothermal reservoirs, and carbon-storage systems [2].

At glacier beds, a series of studies showed that icequakes are best explained by rock-on-rock grinding rather than ice sliding directly over rock or sediment [3, 5, 10, 15, 16, 19]. Fiber cables installed within and beneath glaciers now make it possible to test that picture at unprecedented resolution, including through a full-thickness frozen-in cable at Store Glacier, Greenland [21].

Tools developed in glaciology now support a broader mechanics-based study of earthquakes, volcanoes, landslides, ocean waves, marine acoustics, shallow seafloor structure, and engineered subsurface systems [1, 7, 12, 27]. Across these settings, the common goal is to use dense wavefields and field observations to test the mechanics of deformation and failure at boundaries and during rapid events.

Current work applies fiber sensing to earthquake source physics, volcanic environments including Mount Rainier, Cordón Caulle, and Yellowstone, and shallow offshore imaging. Ocean projects measure surface gravity waves, coupled ocean–solid Earth dynamics, and marine-mammal vocalizations [20, 22, 29, 37]. Through a joint appointment at Pacific Northwest National Laboratory, Brad also contributes to hybrid DAS–seismic monitoring of underground explosions at the Nevada National Security Site, supporting nuclear-test monitoring while advancing controlled-source seismology.

The next phase of the program extends fiber sensing into environments where consequential processes remain poorly observed. A planned 2027–28 Antarctic deployment will target ice-shelf–ocean interaction directly, building on evidence that ocean coupling controls rift propagation and that calving can drive circulation and melt [24, 31].

A second direction examines how freezing changes the growth of water-filled fractures. Field observations and mechanical models will test whether thermomechanical feedbacks regulate hydrofracture and ice-sheet stability, with parallels in magma transport, geothermal systems, and carbon sequestration [2, 32].

A third direction tests whether deep, frozen-in pressure sensors can resolve surface mass balance through tiny changes in overburden pressure. If successful, the method would provide a direct, high-resolution measurement of ice-sheet mass change at depth, building on earlier seismic and mechanical studies of glacier mass [4, 17].