Application of DC Resistivity Imaging to Frozen Ground Investigations

Science of The Total Environment

Lim

Swirad

et al. 2017

This paper presents the results of an investigation into the processes controlling development of a cryo-conditioned rock coast system in Hornsund, Svalbard. A suite of nested geomorphological and geophysical methods have been applied to characterise the functioning of rock cliffs and shore platforms influenced by lithological control and geomorphic processes driven by polar coast environments. Electrical resistivity tomography (ERT) surveys have been used to investigate permafrost control on rock coast dynamics and reveal the strong interaction with marine processes in High Arctic coastal settings. Schmidt hammer rock tests, demonstrated strong spatial control on the degree of rock weathering (rock strength) along High Arctic rock coasts. Elevation controlled geomorphic zones are identified and linked to distinct processes and mechanisms, transitioning from peak hardness values at the ice foot through the wave and storm dominated scour zones to the lowest values on the cliff tops, where the effects of periglacial weathering dominate. Observations of rock surface change using a traversing micro-erosion meter (TMEM) indicate that significant changes in erosion rates occur at the junction between the shore platform and the cliff toe, where rock erosion is facilitated by frequent wetting and drying and operation of nivation and sea ice processes (formation and melting of snow patches and icefoot complexes). The results are synthesised to propose a new conceptual model of High Arctic rock coast systems, with the aim of contributing towards a unifying concept of cold region landscape evolution and providing direction for future research regarding the state of polar rock coasts.

Section: Geophysical Surveysmentioning

confidence: 66%

Cryo-conditioned rocky coast systems: A case study from Wilczekodden, Svalbard

Science of The Total Environment

Lim

Swirad

et al. 2017

“…The properties of the bedrock in the coastal zone were identified with the use of electrical resistivity tomography (ERT). This method is commonly used to detect the presence of permafrost and various types of ground ice (e.g., [40][41][42][43][44][45][46][47]). ERT, which is basically a combination of electrical resistivity sounding and profiling, consists of the measurements of resistivity (R) in a number of four-electrode arrays, in which electric current (I) is transmitted to earth by two electrodes (C 1 , C 2 ), and voltage-potential difference (V) is measured by the second pair of electrodes (P 1 , P 2 ).…”

Section: Methodsmentioning

confidence: 99%

Seawater Intrusion on the Arctic Coast (Svalbard): The Concept of Onshore-Permafrost Wedge

2020

Geosciences

Numerous hydrogeological studies on the coastal zone describe the intrusion of sea water inland, salting underground aquifers. The phenomenon is commonly observed in the coasts outside polar areas. However, the impact of sea water has so far not been an object of detailed investigation in a periglacial environment devoid of subsea permafrost. Geophysical measurements at the west coast of the Wedel-Jarlsberg Land in Svalbard indicate that the border between the unfrozen seabed and the frozen ground onshore is not delimited by the shoreline. A zone of coastal unfrozen ground is located under a thin layer of permafrost reaching toward the sea. This state was observed with the use of electrical resistivity tomography under rocky headlands and capes, uplifted marine terraces located at the foot of mountain massifs and valley mouths as well as in the marginal zone of the Werenskiold Glacier. This short article presents the results of such a measurement, supplemented with electromagnetic detection. The measurements are unique in that they were conducted not only on the land surface, but also at the floor of the sea bay during the low water spring tide. The author proposes name structures detected in the coastal zone as a “permafrost wedge”, extending an identification of the permafrost base between the coast and the glaciers of Svalbard. However, in the absence of boreholes that would allow determining the thermal state of the ground in the study sites, the concept is based only on the interpretation of the geophysical imaging. Therefore, further discussion is required on whether the identified contrasts in electrical resistivity indeed result from thermal differences between the rocks or if they only indicate the cryotic state of the ground (saline cryopeg) within the range of seawater intrusion.

“…We used electrical resistivity tomography (ERT) to identify features of the near-surface ground (Figure 3). This method is commonly used to detect the presence of permafrost (e.g., MacKay, 1969;Hauck, 2002;Ishikawa, 2004;Kneisel & Hauck, 2008 Lewkowicz et al, 2011;Kneisel et al, 2014). During this study, we performed long survey sections (395 m and 315 m, respectively) with 5 m electrode spacing to identify zones of a deep ground thaw in the valley cross-sections (Figure 1a).…”

Section: Geophysical Imagingmentioning

confidence: 99%

“…In the analysis of obtained inversion models, the dependence was used that rocks cooled below a temperature of 0 C drastically reduce their ability to conduct electric current. As practice shows, it is difficult to establish a single resistivity threshold value for frozen and unfrozen ground due to the ground's heterogeneous geological and hydrogeological conditions (e.g., Hauck, 2002;Hayley et al, 2007;Ishikawa, 2004). We set this limit by examining the maximum gradients of the modelled values (Herring & Lewkowicz, 2022).…”

Section: Geophysical Imagingmentioning

confidence: 99%

Spatial and temporal patterns of near‐surface ground temperature in the Arctic mountain catchment

Szymanowski

2023

Land Degrad Dev

We consider the case of a mountain catchment representative of southwest Spitsbergen to investigate the spatial and temporal variation in temperature of the near‐surface ground. We set up 20 thermistor strings distributed in different parts of the catchment, combine the measured data with land surface temperature (LST) retrieved from Landsat imagery, and verify the depth of ground thawing using electrical resistivity tomography. Under current climatic conditions, the thickness of the active layer (ALT) is at least 1.5 m, and in the lower parts of the catchment, between 3.5 and 4 m. The maximum ground surface temperature in the study area can be 27°C, and the temperature at a depth of 1.5 m, 5.4°C. We identified unfrozen ground (taliks) to a depth of 10–30 m in zones of water concentration at foot slopes and under river channels. The persistence of year‐round taliks at lake shores is possible. We verify the hypothesis that topographic parameters significantly determine the spatial variation of near‐surface ground temperature. For each level of temperature aggregation (from 6 h to 12 months data) and each examined the depth of the active layer, it is possible to identify environmental variables—related to energy conditions, heights, terrain relief, and ground surface moisture—significantly correlated with ground temperature, and consequently to specify multiple regression models. Topographic exposure and LST (used only in daily models), altitude, and various approximations of relative height are crucial in their construction. The ground temperature variance, unexplained in the regression analysis, prompts recognition of the critical role of factors not included in the modelling (groundwater, soil structure).