Frozen ground monitoring using DC resistivity tomography

Time-lapse DC resistivity tomography is shown to be a useful method for permafrost and frozen ground monitoring in high-mountain areas. Resistivity changes are related to freezing and thawing processes and monitor the permafrost evolution over monthly to seasonal time scales. A fixed-electrode array allows measurements independent of the snow cover thickness. The 2-dimensional tomographic approach yields information about spatially variable transient processes, such as the advance and retreat of freezing fronts. In combination with borehole temperature data, differences in total water content at different depths could be estimated. In addition, the temporal evolution of the unfrozen water content was calculated showing a strong decrease during the winter months in the near-surface layer and a quasi-sinusoidal behaviour at greater depths. This approach seems promising for future long-term monitoring programmes of the permafrost evolution at low cost.