DAS on Ice: Insights gained from deploying several kilometers of fiber optic cable on Taku Glacier, Alaska

Distributed acoustic sensing (DAS), or the use of fiber optic cables as strainmeters, currently provide valuable data in a range of application but its usefulness for research in the cryosphere remains unclear. DAS allows for a higher spatial density of sensors compared to traditional seismometers but with some decrease in the quality of the data. DAS has the potential to provide valuable insights on outstanding glaciology questions, such as generation of icequakes, the spatiotemporal evolution of subglacial hydrological system, and the dynamics of ice calving events.

To test the usefulness of DAS on ice, in July 2019 we deployed 3.2km of fiber optic cable on Taku Glacier, the largest glacier in the Juneau Icefield. Our cable path included a 1km profile of a basin and then zig zags into the main trunk of Taku. We collected near continuous data for 4.5 days with 16m gauge length, 1m channel spacing, and 500 samples per second. We also conducted an active survey consisting of 41 Betsy gun rounds along the profile in the basin.

From our data, we are able to characterize the surface wave speeds on the glacier as well as identify body waves. The signal from the active survey is visible for several hundred meters away from the individual sources. We stacked repeated shots from the same location in order to boost the signal to noise ratio. This deployment represents a significant first step in exploring what insights can be attained from using DAS in the cryosphere.