Geophysical and Geocryological Investigation of Active Layer Along The North Russian Railway (Khanovey, Russia)

We present a geophysical and geocryological study of permafrost distribution and active layer thickness (ALT) in the Arctic area of Khanovey (Komi Republic, Russia). The area is crossed by a 1.5 km transect of the North Russian Railway that is experiencing serious instabilities caused by subsidence, with vertical deformations up to 2.5 cm/year. This is due to thawing permafrost, a consequence of global warming, whose effects depend on local factors, as vegetation, soil properties and land-use. We performed geocryological surveys including vegetation analysis and underground temperature measurements, together with the less invasive geoelectrical investigation. Results show landscape heterogeneity and an average resistivity of the active layer of about 80 m, while the underlying permafrost shows resistivity values higher than 200 Ωm. Due to the absence of insulating vegetation, low resistivity (<80 m) permanent unfrozen ground (i.e. talik and thermokarst lakes) occurs close to the railroad. In the study area, ALT values range between 0.5 m and 7 m. These detailed information on specific spatial variation in cryological conditions are fundamental to address the design of engineering solutions to ensure structural stability of the railway, such as maintenance of the thermal balance of the ground.