| 14 Sep 2026
Lithological controls on seasonal freeze–thaw dynamics in coastal Antarctic permafrost: Insights from three years of continuous geophysical monitoring
Abstract. An automated electrical resistivity tomography (A-ERT) system was installed in the vicinity of the Czech Johann Gregor Mendel Station on James Ross Island, Antarctica, in March 2023. The 23 m long transect crosses a lithological boundary between fine-grained Cretaceous sedimentary rocks and coarser marine terrace deposits, with daily electrical resistivity measurements complemented by environmental observation data. The aim of this study was to characterize the freeze–thaw dynamics of the active layer and explore the relationship between thermal, hydrological, and geoelectrical parameters in a geologically complex coastal permafrost environment. Three years of continuous monitoring have demonstrated that the two lithological units are markedly distinct in their geoelectrical response, with the electrical resistivity values consistently higher within the marine terrace section. In both lithologies, close relationships between electrical resistivity and ground temperature, as well as with soil moisture, were identified. A slight freezing point depression was detected, at −0.1 °C within the marine terrace deposits and −0.3 °C within the Cretaceous sediments. Tracking the progression of the thaw front was possible within the Cretaceous sediments using the gradient method; however, this proved challenging within the marine terrace deposits due to a greater vertical heterogeneity. This research demonstrates the usefulness of A-ERT as a tool for active layer and permafrost monitoring in complex settings, where traditional point- or borehole-based methods may not adequately represent spatial variability.
Competing interests: At least one of the (co-)authors is a member of the editorial board of The Cryosphere.
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1. This paper provides a thorough report on the 2D automated electrical resistivity tomography (A-ERT) data near the Czech Johann Gregor Mendel Station on James Ross Island, Antarctica over a three year period. Together with other sensors, the freeze-thaw dynamics of the sites is studied (particularly in terms of active layer thickness, ALT) and revealed strong lithological controls. I think the paper is written clearly and concisely, with clear objectives and research questions that are addressed later on in the results and discussions. However, it would benefit from being clearer about its novelty, whether it is in terms of ERT monitoring and analysis methods, or process understanding of freeze-thaw cycles at the site, in Antarctica, or in permafrost more generally.
2.There have been many recent papers on the use of ERT to study freeze-thaw cycles in the Cryosphere, which will be helpful to include
Cimpoiasu, M.O., Kuras, O., Harrison, H., Wilkinson, P.B., Meldrum, P., Chambers, J.E., Liljestrand, D., Oroza, C., Schmidt, S.K., Sommers, P., Vimercati, L., Irons, T.P., Lyu, Z., Solon, A., Bradley, J.A., 2025. High-resolution 4D electrical resistivity tomography and below-ground point sensor monitoring of High Arctic deglaciated sediments capture zero-curtain effects, freeze–thaw transitions, and mid-winter thawing. The Cryosphere 19, 401–421. https://doi.org/10.5194/tc-19-401-2025
Scandroglio, R., Weber, S., Limbrock, J.K., Krautblatter, M., 2026. Field-validated imaging of decadal and seasonal changes in permafrost bedrock using quantitative electrical resistivity tomography (Zugspitze, Germany/Austria). The Cryosphere 20, 4787–4809. https://doi.org/10.5194/tc-20-4787-2026
Murton, J.B., Kuras, O., Krautblatter, M., Cane, T., Tschofen, D., Uhlemann, S., Schober, S., Watson, P., 2016. Monitoring rock freezing and thawing by novel geoelectrical and acoustic techniques. JGR Earth Surface 121, 2309–2332. https://doi.org/10.1002/2016JF003948
Uhlemann, S., Dafflon, B., Peterson, J., Ulrich, C., Shirley, I., Michail, S., Hubbard, S.S., 2021. Geophysical Monitoring Shows that Spatial Heterogeneity in Thermohydrological Dynamics Reshapes a Transitional Permafrost System. Geophysical Research Letters 48, e2020GL091149. https://doi.org/10.1029/2020GL091149
Uhlemann, S., Wang, C., Wielandt, S., Fiolleau, S., Ulrich, C., Shirley, I., Dafflon, B., 2025. Geophysical monitoring of hydrological dynamics within a discontinuous permafrost environment. https://doi.org/10.5194/egusphere-egu25-12367
3. Why is the inversion done with Res2Dinv in Fig 4 but the rest is done using pyGimLi?
4. L175: how was the 4% error level being decided? Was the error levels stable throughout the 3-year monitoring period?
5.Have the authors considered the effect of a thick snow layer in their ERT inversions? A snowpack with melting snow water will have lower resistivity than air?
6.If gradient method is not working well, perhaps the authors could try a clustering method (e.g. Cimpoiasu et al. 2025)?