Michael R Prior-Jones, Elizabeth Bagshaw, Jonathan M Lees , Lindsay Clare, Stephen Burrow, Mauro A Werder, Nanna B Karlsson, Dorthe Dahl-Jensen, Tom Chudley , Poul Christoffersen

Subglacial hydrological systems require innovative technological solutions to access and observe. Wireless sensor platforms can be used to collect and return data, but their performance in deep and fast-moving ice requires quantification. We report experimental results from Cryoegg: a spherical probe that can be deployed into a borehole or moulin and transit through the subglacial hydrological system. The probe measures temperature, pressure and electrical conductivity in-situ and returns all data wirelessly via a radio link. We demonstrate Cryoegg’s utility in studying englacial channels and moulins, including in-situ salt dilution gauging. Cryoegg uses very high frequency (VHF) radio to transmit data to a surface receiving array through up to 1.3 km of cold ice - a significant improvement on the previous design. The wireless transmission uses Wireless M-Bus on 169 MHz; we present a simple radio link budget model for its performance in cold ice and experimentally confirm its validity. Cryoegg has also been tested successfully in temperate ice. The battery capacity allows measurements to be made every two hours for more than a year. Future iterations of the radio system will enable Cryoegg to transmit data through up to 2.5 km of ice.

The published version is available open access from Journal of Glaciology at https://doi.org/10.1017/jog.2021.16