Autonomous rover enables radar profiling of ice-fabric properties in Antarctica

A ground-penetrating radar is an extensively used geophysical tool in cryosphere sciences (ice sheets and glaciers) with sounding depths of several kilometers due to the small radio-wave attenuation in ice sheets. The detection of the ice thickness and internal ice stratigraphy with commercial radars has become standard. However, there is still an observational gap in determining dielectric and mechanical ice-fabric anisotropy and basal properties using these systems. Recently, a ground-based phase-coherent radar showed its potential to fill this gap. However, this requires that the corresponding ground-based radars cover profiles several tens of kilometers in length. We address this challenge by modifying an autonomous rover to collect phase-coherent, quad-polarimetric radar data geolocated with real-time kinematic (RTK) positioning. In a proof-of-concept study in Antarctica, we demonstrate that this allows the collection of quad-polarimetric data along a 23-km profile, mapping anisotropic ice-fabric properties at <100-m intervals across the transition of grounded to floating ice. This study shows the possibility of collecting data that will refine ice-flow models by providing missing rheological parameters. This work also demonstrates the versatility of the autonomous ground vehicle with its ability to tow more than 200-kg payload, with a battery run time of over 6 h, and with a modular design that enables future integration of different radars or other geophysical sensors

Design and Performance of the Hotrod Melt-Tip Ice-Drilling System

We introduce the design and performance of a melt-tip ice-drilling system designed to insert a temperature sensor cable into ice. The melt tip is relatively simple and low cost, designed for a one-way trip to the ice-bed interface. The drilling system consists of a melt tip, umbilical cable, winch, interface, power supply, and support items. The melt tip and the winch are the most novel elements of the drilling system, and we make the hardware and electrical designs of these components available open access. Tests conducted in a laboratory ice well indicate that the melt tip has an electrical energy to forward melting heat transfer efficiency of ~35 % with a theoretical maximum penetration rate of ~12 m/hr at maximum 6.0 kW power. In contrast, ice-sheet testing suggests the melt tip has an analogous heat transfer efficiency of ~15 % with a theoretical maximum penetration rate of ~6 m/hr. We expect the efficiency gap between laboratory and field performance to decrease with increasing operator experience. Umbilical freeze-in due to borehole refreezing is the primary depth-limiting factor of the drilling system. Enthalpy-based borehole refreezing assessments predict refreezing below critical umbilical diameter in ~4 hours at -20 ˚C ice temperatures and ~20 hours at -2 ˚C. This corresponds to a theoretical depth limit of up to ~200 m, depending on firn thickness, ice temperature and operator experience.</p