Seismic Tremor Reveals a Hidden Water Reservoir in Tête Rousse Glacier

In May 2022, a dense seismic network deployed on the glacier recorded a persistent harmonic tremor in the 20–200 Hz frequency range, starting shortly after air temperatures rose above 0 °C. The tremor amplitude was strongest in the evening and showed a clear correlation with water-level variations measured in a crevasse located 230 m downglacier, with a time delay consistent with meltwater infiltration through snow and ice.

Using complementary seismic approaches, including spectral analysis, template matching, and source localization based on amplitude decay and P–S wave arrivals, the researchers consistently located the tremor source near the bergschrund in the upper part of the glacier. Importantly, ground-penetrating radar surveys conducted in 2024, followed by borehole investigations, confirmed the presence of a water-filled reservoir close to the tremor location.

The characteristics of the signal, stable resonance frequencies, shallow source depth, and lack of regular repeating events, indicate that the tremor is most likely generated by water-level variations within a fracture connected to the reservoir, rather than by basal sliding. This interpretation is further supported by the strong temporal link between tremor amplitude, temperature, and water pressure.

This study highlights the potential of seismic monitoring as a non-invasive tool to identify and track englacial water reservoirs, complementing radar and borehole surveys. Such approaches are particularly valuable for improving the early detection of potentially hazardous water pockets in glaciers affected by climate warming.