Basal hydrology of fast Greenlandic glacier captured using passive seismic network

The acceleration of fast-flowing, marine-terminating glaciers and the steady increase in surface run-off are the two most influential factors affecting present-day ice loss from the Greenland Ice Sheet. Because almost all surface meltwater is transported to the glacier bed, basal hydrological conditions are directly influenced by surface processes. Studying the relationships between surface run-off, basal hydrology, and ice flow velocity is therefore essential to understanding the effects of climate change on the contribution of marine-terminating glaciers to global sea-level rise. Passive seismology enables the continuous observation of a range of glacio-hydrological phenomena, including icequakes, hydrofractures, and tremors associated with water transport. To investigate the effects of variations in water input over the course of several melt seasons, a network of 12 near-surface and 3 deep borehole geophones was deployed on Store Glacier, a fast-flowing, marine-terminating glacier in West Greenland. The network, part of the multidisciplinary RESPONDER project, recorded continuously throughout May-October 2018 and May-July 2019. Here, we present results in the form of spectrograms, RMS amplitude, and microseismic event locations, capturing a variety of phenomena including rapid supraglacial lake drainage events, crevassing, rainfall, the onset and termination of the summer melt season, and impulsive basal microseismic activity. In particular, seismic and GPS recordings of a partial lake drainage event place constraints on the magnitude (~0.1 m) and extent (3-4 km) of ice sheet uplift and fracturing downstream of the drainage site. We also observe changes in seismic amplitude and frequency content consistent with glacial responses to increased transfer of surface water to the bed. Our data shows that the interaction between basal hydrology and fast glacier flow can be captured using a passive seismic network.