Tidally Modulated Glacial Seismicity at the Foundation Ice Stream, West Antarctica

We investigate the occurrence of repeating glacial seismicity near the grounding line of the Foundation Ice Stream and further upstream using continuous broadband seismic data collected by Polar Earth Observing Network (POLENET/A-NET) stations from 2014 through 2019. Through manual identification and cross-correlation analysis, 2,237 discrete icequakes (1.5=M-L = 2.6) are detected in two spatial clusters, one located at the grounding line of the Foundation Ice Stream (2,219 event detections) and a second located further upstream proximal to a subglacial ridge (18 event detections). Seismicity is predominantly concentrated in the Schmidt Hills, located adjacent to the grounding line of the Foundation Ice Stream, and shows clear ocean tide modulation. Seismic events primarily occur during spring tides, and, on a shorter timescale, concurrent with the rising tide preceding daily maximum high tide. The seismicity can be attributed to stick-slip motion and fracturing that preferentially occur during rising tides. Seismicity located further upstream in the southern portion of the Foundation Ice Stream most likely reflects basal stick-slip processes associated with the subglacial topographic high.