Seismic monitoring of the Rutor proglacial stream: exploring the impact of glacier dynamics on water flow and bedload transport processes

An important consequence of the rapid retreat of Alpine glaciers associated with global warming is the increasing extent of proglacial areas. These environments are dominated by a heterogeneous and dynamic fluvial system, whose evolution mostly depends on the interplay between the varying water discharge and coarse sediment supply coming from the glacier terminus. Although understanding the impact of glacier retreat on bedload yield is essential for the preservation of high-mountain regions, long-lasting investigations on the processes occurring in proglacial areas are lacking. In this context, seismic sensors recording river-induced ground vibrations have been shown to constitute a valid monitoring technique (Mancini et al., 2023; Corte et al., 2024).

Here, we present the results of monitoring campaigns carried out in the proglacial area of the Rutor Glacier (Aosta Valley, Italy) during the ablation seasons of the last three years. Ground vibrations have been monitored using a network of three geophones installed next to a stable reach of the main proglacial torrent  ∼150 m downstream of the glacier mouth. Direct measurements of bedload transport have been made in 2022 and 2023 by deploying portable bedload traps at the glacier mouth. In addition to meteorological data gathered at a weather station, water discharge has been estimated by means of a downstream gauge station. We have found that a varying and non-trivial relationship exists between the direct bedload measurements and the recorded seismic signals, indicating a potential strong buffering of sediment export exerted by the proglacial area. Moreover, for all the three monitoring campaigns but starting at different moments of the ablation season, we have observed quasi-periodic peaks of seismic power occurring at a sub-hourly scale during the afternoon. We advance that they could be related to water discharge fluctuations resulting from the dynamics of the subglacial drainage system. These observations show the effectiveness of using seismic methods to shed some light on the complex feedback mechanisms existing between glacier dynamics and the natural processes of proglacial areas.

References

Mancini, D., Dietze, M., Müller, T., Jenkin, M., Miesen, F., Roncoroni, M., et al. (2023). Filtering of the signal of sediment export from a glacier by its proglacial forefield. Geophysical Research Letters, 50, e2023GL106082. https://doi.org/10.1029/2023GL106082

Corte, E., Ajmar, A., Camporeale, C., Cina, A., Coviello, V., Giulio Tonolo, F., Godio, A., Macelloni, M. M., Tamea, S., and Vergnano, A. (2024): Multitemporal characterization of a proglacial system: a multidisciplinary approach, Earth Syst. Sci. Data, 16, 3283–3306, https://doi.org/10.5194/essd-16-3283-2024