Seismic insights into the subglacial hydrology in the vicinity of Sermeq Kujalleq in Kangia, Greenland

Sermeq Kujalleq in Kangia (SKK) in West Greenland is one of the fastest moving glaciers in the world, with a flow speed up to 30–40 meters per day, resulting in a large outflux of ice into the ocean. Our project investigates the dynamical behavior of SKK and its interaction with the surrounding slow-moving ice. To that aim, passive seismic and other geophysical field campaigns spanning the summer 2022 were conducted on the slow-moving ice, in the vicinity of the fast ice-stream.

In this study, we use continuous seismic field measurements combined with Global Navigation Satellite System(GNSS) measurements to investigate the summer subglacial processes of SKK over a three-month period. Seismic horizontal-to-vertical spectral ratios (HVSR) were used to capture subglacial changes, while GNSS receivers tracked surface velocities. At the end of June, we observed the appearance of a low-frequency resonance peak in the HVSR data that is present until the end of July. At the same time, our analysis revealed a ~20% speed-up in ice flow and ~8 cm of vertical uplift, coinciding with simulated elevated subglacial water pressures and water storage. Notably, the HVSR time series clearly detects the start of the melt season, marked by a shift from a coupled state, where the glacier is in contact with the bed, to a partially decoupled state characterized by inefficient subglacial drainage and reduced basal friction.

Numerical modeling based on elasticity equations further validated these observations, linking lower resonance frequencies with the decoupling process. This study highlights the potential of HVSR to detect rapid subglacial transitions from a coupled to a partially decoupled state. These findings also demonstrated that glaciated areas surrounding ice streams, though slow-moving, can exhibit fast-changing dynamics.