Active Layer and Permafrost Investigations Using Geophysical and Geocryological Methods—A Case Study of the Khanovey Area, Near Vorkuta, in the NE European Russian Arctic

Abstract

Permafrost in the NE European Russian Arctic is suffering from some of the highest degradation rates in the world. The rising mean annual air temperature causes warming permafrost, the increase in the active layer thickness (ALT), and the reduction of the permafrost extent. These phenomena represent a serious risk for infrastructures and human activities. ALT characterization is important to estimate the degree of permafrost degradation. We used a multidisciplinary approach to investigate the ALT distribution in the Khanovey railway station area (close to Vorkuta, Arctic Russia), where thaw subsidence leads to railroad vertical deformations up to 2.5 cm/year. Geocryological surveys, including vegetation analysis and underground temperature measurements, together with the faster and less invasive electrical resistivity tomography (ERT) geophysical method, were used to investigate the frozen/unfrozen ground settings between the railroad and the Vorkuta River. Borehole stratigraphy and landscape microzonation indicated a massive prevalence of clay and silty clay sediments at shallow depths in this area. The complex refractive index method (CRIM) was used to integrate and quantitatively validate the results. The data analysis showed landscape heterogeneity and maximum ALT and permafrost thickness values of about 7 and 50 m, respectively. The active layer was characterized by resistivity values ranging from about 30 to 100 Ωm, whereas the underlying permafrost resistivity exceeded 200 Ωm, up to a maximum of about 10 kΩm. In the active layer, there was a coexistence of frozen and unfrozen unconsolidated sediments, where the ice content estimated using the CRIM ranged from about 0.3 – 0.4 to 0.9. Moreover, the transition zone between the active layer base and the permafrost table, whose resistivity values ranged from 100 to 200 Ωm for this kind of sediments, showed ice contents ranging from 0.9 to 1.0. Taliks were present in some depressions of the study area, characterized by minimum resistivity values lower than 10 Ωm. This thermokarst activity was more active close to the railroad because of the absence of insulating vegetation. This study contributes to better understanding of the spatial variability of cryological conditions, and the result is helpful in addressing engineering solutions for the stability of the railway.

Mapping Permafrost Variability and Degradation Using Seismic Surface Waves, Electrical Resistivity, and Temperature Sensing: A Case Study in Arctic Alaska

“…Alternatively, the distinct lithology and soil mineral composition within this zone could be significantly influencing the resistivity and seismic velocity properties of unfrozen sediments in the near‐surface, as highlighted in studies by Rossi et al. (2022) and Accaino et al. (2023), respectively.…”

“…First, it is plausible that this zone remains frozen, with its temperature lingering below the freezing point of cryopegs. Alternatively, the distinct lithology and soil mineral composition within this zone could be significantly influencing the resistivity and seismic velocity properties of unfrozen sediments in the near-surface, as highlighted in studies by Rossi et al (2022) and Accaino et al (2023), respectively. These findings are aligned with previous studies demonstrating the complex and heterogeneous nature of permafrost in the study site (Brown, 1969;Dafflon et al, 2016).…”

Best practices for using electrical resistivity tomography to investigate permafrost

“…However, 2D surveying may not adequately capture heterogeneity across a site, and can be affected by out‐of‐plane features 141 . 2D profiles can be used to visualize 3D structures by collecting several 2D profiles and displaying them together in 3D space 114,142 or by interpolating between adjacent 2D profiles, 143 which is sometimes referred to as 2.5D surveying. 3D resistivity surveying can be approached in two main ways.…”

“…3D surveying has been used in permafrost research to examine heterogeneous 3D landforms such as ice wedge polygons, 43 rock glaciers, 145 and palsas 146 . 3D approaches also have the advantage of being able to estimate permafrost volume 134,143 …”

“…146 3D approaches also have the advantage of being able to estimate permafrost volume. 134,143 7.4 | 3D surveying: a case study from Switzerland ERT's utility in estimating permafrost distribution and quantifying changes in frozen bedrock.…”