Seismic monitoring of grounding line processes at Totten Glacier, East Antarctica

The Aurora Subglacial Basin (ASB), East Antarctica, contains approximately 3.5m global sea-level equivalent of marine-based ice, which primarily drains through Totten Glacier. The dynamics of Totten Glacier are therefore a major influence on mass balance for the East Antarctic Ice Sheet (EAIS). The grounding line geometry is complex, and has undergone rapid migration over the past decades, with upstream regions of retrograde bed slope potentially leaving the glacier vulnerable to the marine ice sheet instability if the grounding line were to retreat beyond the Vanderford Trench. Enhanced monitoring capability for Totten Glacier, particularly in this grounding line region, is therefore of pivotal importance for assessing the future stability of the EAIS. 

Passive seismology offers a method for detecting and analysing transient or hidden glaciological processes such as stick-slip basal motion, iceberg calving, ice fracture, and subglacial hydrology. In this work, we present results from a seismic network deployed near the grounding line of Totten Glacier during the austral summer of 2018-19. Thousands of seismic events are coherently detected and catalogued across the network. We use template matching methods to compile a database of the repeating event waveforms and analyse their timing, magnitudes and inter-event durations. Such multiplet events are of particular note in this study, where the near identical waveforms are best explained by a repeating source mechanism. This is interpreted as being due to repeated slip of the glacier at asperities at the glacier bed near the grounding line. The seismic waveforms are used to investigate the underlying physics of the repeating events, comparing the underlying slipping processes active in the grounding zone to tectonic analogues. Analysis of these repeating events has the potential to elucidate the basal sliding processes key to the dynamics of this large outlet glacier.