Seismic observations of supraglacial lake drainage in the near-terminus region of Helheim Glacier, Greenland

We use data from a seven-week deployment of seismometers installed at bedrock sites surrounding southeast Greenland's Helheim Glacier to examine high-frequency seismicity in the lowermost 20 km of the glacier. We detect icequakes automatically using an envelope-based approach. We evaluate changes in icequake productivity together with independent constraints from satellite imagery and other auxiliary datasets. Near the calving front, changes in icequake productivity are dominated by a large calving event that also produces a glacial earthquake. Productivity is also strongly tidally modulated. Farther upglacier, icequake productivity shows several large excursions observable on multiple seismic stations. Some of these spikes in seismic activity are associated with drainage of a supraglacial lake. We track the signal across multiple stations and evaluate the temporal characteristics of the variability in productivity due to lake drainage. This allows us to gather additional insight into the hydrology of a major Greenland outlet glacier, and the effects of short-term variations in hydrology on the dynamics of the glacier.