Cryoegg: development and field trials of a wireless subglacial probe for deep, fast-moving ice

Michael R Prior-Jones,Stephen Burrow,Nanna B Karlsson,Thomas R Chudley,Jemma L Wadham,Mauro A Werder,Samuel H Doyle,Poul Christoffersen,Dorthe Dahl-Jensen,Lindsay Clare,Jonathan Lees,Bryn Hubbard,Elizabeth A Bagshaw

doi:10.1017/jog.2021.16

Abstract

AbstractSubglacial 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 VHF radio to transmit data to a surface receiving array. We demonstrate transmission 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 should allow measurements to be made every 2 h 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.

Highlights

The presence and behaviour of liquid water in the subglacial environment govern the response of ice to climate warming
The defining feature of these different drainage configurations is the water pressure: channelised systems operate at lower pressure than linked cavities, measurement of the subglacial water pressure can be used to determine the likely structure of the drainage system, and the acceleration response of the ice to increased surface melt inputs
We describe the redesign of Cryoegg to give enhanced radio link performance and show the outcomes of field trials at sites in Greenland and the Swiss Alps

Summary

Introduction

The presence and behaviour of liquid water in the subglacial environment govern the response of ice to climate warming. In the melt season, an increased flux of meltwater is routed to the bed and the low capacity, inefficiently linked cavity system is forced to expand, forming efficient channels that can transport substantial volumes of water. This reduces the area of the bed in contact with water, and potentially regulates the flow of ice (Sole and others, 2011; Tedstone and others, 2015; Nienow and others, 2017; Flowers, 2018). The defining feature of these different drainage configurations is the water pressure: channelised systems operate at lower pressure than linked cavities, measurement of the subglacial water pressure can be used to determine the likely structure of the drainage system, and the acceleration response of the ice to increased surface melt inputs

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