Ice mass discharge through the Antarctic subglacial hydrographic network as a trigger for cryo-seismicity

We analyze seismic time series collected during experimental campaigns in the area of the David Glacier, VictoriaLand, Antarctica, between 2003 and 2016. We observe hundreds of repeating seismic events, characterized by highly correlated waveforms (cross-correlation > 0.95), which mainly occur in the grounding zone, i.e. the region where the ice transitions from grounded ice sheet to freely floating ice shelf. The joint analysis of seismic events and observed local tidal measurements suggests that seismicity is not only triggered by a regular, periodic driver such as the ocean tides but also morelikely by transient pulses. We consider potential environmental processes and their impact on the coupling between the glacier flow and the bedrock brittle failure. Among the environmental variables examined, our findings suggest that clustered andrepeated seismic events may be related to transient episodes of ice-mass discharge correlated to a change in the subglacialhydrographic system that originates upstream of the glacier, lubricating the interface with the bedrock. This hypothesis issupported by the gravity variation observations provided by the GRACE satellite mission, which observed mass variationsduring periods characterized by seismic clustering.