Instrumentation used for polar science is subject to extreme technological challenges, which must be overcome to understand how the Earth is responding to climate change. This project will enable the investigation of one of the last frontiers on planet Earth: subglacial environments, the cold, dark, high pressure zones beneath kilometres of ice. These environments control how ice responds to increasing temperatures and contribute to rising sea levels, but are by nature extremely challenging to measure. The presence of liquid water in this sensitive zone can have a significant impact on ice sheet behaviour, but measuring and characterising the water is presently impossible. Our capacity for predicting future environmental change is therefore severely limited by a lack of suitable instrumentation, so this project will develop a unique sensor to measure liquid water beneath deep ice sheets.
Subglacial environments are investigated via narrow (<150 mm diameter) boreholes drilled by ice corers or melted by hot water jets. Traditionally, cabled sensors are implanted in the boreholes and measurements sent to the surface. In fast flowing sectors of ice sheets, however, the use of cabled sensors is problematic. Rapidly deforming ice severs connections with the surface, and retrieval of the sensors through a non-vertical shaft is impossible. Wireless sensors are therefore the only alternative, since they can transmit data without a physical connection. Radio frequency (RF) techniques have long been used to probe features within and beneath ice, and more recently, to transmit data through up to 2.5 km of cold, dry ice and 600 m of temperate, wet ice. RF is therefore a viable solution for transferring measured data to the surface, but the transmission properties of ice must be fully characterised before an appropriate transmission-receiver scheme can be designed and tested.
The design requirements for the sensor are complex but achieveable. It must be able to collect fundamental measurements of water beneath up to 2.5 km of ice, be free to move within meltwater present beneath the ice, and transmit data to the surface. The sensor suite must be able to operate in low temperature, high pressure conditions, with no external power supply for up to 12 months. The RF transmission must be efficient, able to pass through mixed media (ice, sediment, water, cracks), and received and recorded at the surface by a low power, small footprint receiver which can operate for prolonged timescales.
The project will build on previous research, which designed and tested prototype sensors for shallow ice applications. These were successful in the target environment, but cannot transmit through the deeper sectors of ice which ultimately influence global sea levels. The project must improve and optimise our prototypes through a targeted laboratory and field testing campaign, which will select a suitable sensor set, design a transmission scheme, and manufacture a sensor package which can measure liquid water beneath 2.5 km of ice and send data to the surface. The prototype developed by this proposal will be deployed at two locations in Greenland to measure subglacial meltwater. Through partnership with two international scientific programs, we can test and deploy the Deep Cryoegg via boreholes drilled into the ice sheet, to reveal important information about how ice sheets are responding to increasing temperatures. The project will harness RF Communications to collect data that will predict future environmental changes, and provide a crucial contribution to helping the UK Live with Environmental Change.
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