Time‐Lapse Capacitive Resistivity Imaging — A Novel Methodology for the Monitoring of Permafrost Processes in Bedrock

Abstract

The British Geological Survey, in partnership with the Universities of Sussex and Bonn, is investigating and seeking to prove a new technology concept for the non‐invasive volumetric imaging and routine temporal monitoring of the thermal state of permafrost, a key indicator of global climate change. Capacitive Resistivity Imaging (CRI), a technique based upon a low‐frequency, capacitively‐coupled measurement approach (Kuras et al., 2006) is applied in order to emulate Electrical Resistivity Tomography (ERT) methodology, but without the need for galvanic contact on frozen soils or rocks. Recent work has shown that temperature‐calibrated ERT using galvanic sensors is capable of imaging recession and re‐advance of rock permafrost in response to the ambient temperature regime (Krautblatter et al., 2010). However, the use of galvanic sensors can lead to significant practical limitations on field measurements due to high levels of and large variations in contact resistances between sensors and the host material as it freezes and thaws. The capacitive technology developed here overcomes this problem and provides a more robust means of making high‐quality resistance measurements with permanently installed sensors over time. Reducing uncertainty due to uncontrolled noise from galvanic sensors increases the value of time‐lapse ERT datasets in the context of monitoring permafrost.