Distributed Acoustic Sensing (DAS) of Seismic Properties in a Borehole
drilled on a Fast-Flowing Greenlandic Outlet Glacier
Abstract
Distributed acoustic sensing (DAS) is a new technology in which seismic
energy is recorded at high spatial and temporal resolution along a
fibre-optic cable. We show analyses from the first glaciological
borehole deployment of DAS to measure the englacial and subglacial
seismic properties of Store Glacier, a fast-flowing outlet of the
Greenland Ice Sheet. By characterizing compressional and shear wave
propagation in 1030 m-deep vertical seismic profiles, sampled at 10 m
vertical resolution, we detected a transition from isotropic to
anisotropic ice consistent with a Holocene-Wisconsin transition at 83%
of the ice thickness. We also infer temperate ice in the lowermost 100 m
of the glacier, and identified subglacial reflections originating from
the base of a 20 m-thick layer of consolidated sediment. Our findings
highlight the transformative potential of DAS to inform the physical
properties of glaciers and ice sheets.