Spectral induced polarization imaging to monitor seasonal and annual dynamics of frozen ground at a mountain permafrost site in the Italian Alps

• Published in: The Cryosphere
• Main Authors: T. Maierhofer, A. Flores Orozco, N. Roser, J. K. Limbrock, C. Hilbich, C. Moser, A. Kemna, E. Drigo, U. Morra di Cella, C. Hauck
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2024
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Ice; permafrost; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-18-3383-2024; https://doaj.org/article/f4114f79a2e24e1c8559755e42c095e5

We investigate the application of spectral induced polarization (SIP) monitoring to understand seasonal and annual variations in the freeze–thaw processes in permafrost by examining the frequency dependence of subsurface electrical properties. We installed a permanent SIP monitoring profile at a high-mountain permafrost site in the Italian Alps in 2019 and collected SIP data in the frequency range between 0.1–75 Hz over 3 years. The SIP imaging results were interpreted in conjunction with complementary seismic and borehole data sets. In particular, we investigated the phase frequency effect ( ϕ FE ), i.e., the change in the resistivity phase with frequency. We observe that this parameter ( ϕ FE ) is strongly sensitive to temperature changes and might be used as a proxy to delineate spatial and temporal changes in the ice content in the subsurface, providing information not accessible through electrical resistivity tomography (ERT) or single-frequency IP measurements. Temporal changes in ϕ FE are validated through laboratory SIP measurements on samples from the site in controlled freeze–thaw experiments. We demonstrate that SIP is capable of resolving temporal changes in the thermal state and the ice / <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="8pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="57ee8123d9c9aefcf23d9c7f6463c158"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-18-3383-2024-ie00001.svg" width="8pt" height="14pt" src="tc-18-3383-2024-ie00001.png"/></svg:svg> water ratio associated with seasonal freeze–thaw processes. We investigate the consistency between the ϕ FE observed in field data and groundwater and ice content estimates derived from petrophysical modeling of ERT and seismic data.