Monitor the subglacial drainage system beneath the surging Bering Glacier with ambient seismic noise

Surge-type glaciers provide us a unique opportunity in understanding the mechanisms of fast ice flows. However, the spatial configuration of subglacial drainage system, which plays a critical role during glacier surges, is inaccessible to most field methods. Here I apply seismic noise interferometry to the Bering Glacier, Alaska, to monitor its drainage system, covering its latest surge event from 2008 to 2011. I observe substantial frequency-dependent drops of Rayleigh and Love wavespeeds during the surge event, caused by changes of the basal conditions. Furthermore, the magnitudes of the speed changes for Rayleigh and Love waves require an anisotropic basal layer that is best explained by linked basal crevasses.