Borehole Instrument Design for Deployment on the Athabasca Glacier

Observing basal processes of glaciers and ice sheets poses numerous logistical, financial, and technical design challenges. Here, we seek to design, build, and deploy 12 low-cost borehole instrument strings on the Athabasca Glacier to record several datasets of interest. The scientific goals of this project are to observe the internal ice deformation of boreholes drilled to the glacier bed in an effort to constrain basal sliding rates. Additionally, we seek to measure water pressure and electrical conductivity near the bed to understand subglacial hydraulic and sediment fluxes. Critical specifications considered in designing the borehole instrument strings included the ability to withstand a water submersion depth of up to 300 meters, sensor adhesion to the drilled borehole, and cost minimization. The power and data logging equipment for each instrument string on the surface of the glacier must be able to withstand a harsh mountain environment with high winds and temperatures reaching -30 degrees Celsius. We modify an open source tiltmeter design consisting of an Arduino microcontroller, a Sparkfun three-axis tilt chip, and a printed circuit board housing the data communication and power regulation components. A secondary sensor design consisting of these components, a 500 PSI piezometer, and an Atlas conductivity sensor was also developed. These sensors are housed in PVC, cast in electronics grade epoxy, and communicate along a common, twisted pair transmission line to Northern Widget data loggers on the surface. Data transmission utilizes a half-duplex, RS-485 logic to allow for long distance communication to and from the bed of the glacier. Each instrument string consists of five tilt-only sensors spaced in the upper part of the borehole and two tilt sensors with pressure and conductivity capabilities near the bed. These instrument strings were deployed in boreholes drilled to the bed of Athabasca Glacier in July of 2022 and are currently collecting their respective datasets.