Home – Home – Jornals – Earth’s Cryosphere 2025 number 5

Climate changes in permafrost regions lead to noticeable alteration of the environmental conditions, including, in particular, an increase in permafrost temperature and depth of seasonal thaw and an activation of exogenous cryogenic processes. This paper presents the results of monitoring the active layer thickness and vertical surface displacements at the Circumpolar Active Layer Monitoring (CALM) site Lavrentiya located in the area of the “Eastern Chukotka Coastal Plains” research station. Under conditions of the increased summer heat supply over the period of 2004-2024, the rate of ground surface subsidence varied from 1.4 to 3.5 cm/yr, while changes in the active layer thickness (ALT) were from -3.2 to +1.6 cm/yr. The ground surface subsidence took place due to the isotropic thawing of the ice-rich transient layer of the soil-permafrost complex without the formation of thermokarst landforms. Thus, against the background of relatively stable variations in the ALT, a gradual unidirectional subsidence of the surface caused by the progressive thawing of the transient and intermediate layers was observed. The results highlight a significant underestimation of the rates of permafrost table deepening obtained by the traditional mechanical probing method.

The results of experimental studies of the influence of the initial freezing conditions and heating-cooling cycles of a finely dispersed model soil (kaolinite clay in a fully water-saturated state with the moisture content of 0.43-0.51) on its water filtration properties in the frozen state are presented. The filtration capacity of frozen kaolinite clay depends not only on its temperature but also on the freezing conditions. Graphs of the water permeability coefficient of the frozen soil versus temperature in the range of -0.05…-0.3 °C have been obtained for various soil freezing conditions. These graphs demonstrate the significant influence of freezing conditions on the filtration properties of frozen soil. Experimental research in this area is important for predicting the behavior of frozen heavy-textured soils near the initial freezing temperature, which is especially relevant in a changing climate.

Landscape-hydrological and hydrogeological changes have been studied in a second-order creek valley with water recharge taliks formed along two linear faults and an isometric depression closing the lower fault. A hypothesis about the tectonic origin of these changes is advanced based on the analysis of aerospace materials, in situ observations, and reference data. At least until 1965, there was no runoff in the valley downstream of the depression, and the maximum water infiltration rate exceeded 4 m³/s. Surface water infiltration, together with the deposition of sediment load, took place mainly in the depression. Subsequently, both processes virtually stopped there because of the rise of the bottom of the depression relative to the valley thalweg, and a fully developed channel was shaped downstream. Surface water infiltration has decreased by more than an order of magnitude and is observed now mainly in the area of linear faults. In the depression, it occurs sporadically at its margin, where a tectonic ditch is perpendicular to the creek channel. The ongoing tectonic activity may cause high intensity of water intake, up to the spontaneous discharge of the channel flow. In the observed case, such a discharge flow developed in the channel in the direction opposite to the slope of the creek thalweg. Such spontaneous phenomena cannot be explained within the framework of modern concepts about the minimum size of mobile tectonic blocks and attest to the need for their revision.

A design and technological solution to modify the soil temperature regime and maintain the upper boundary of permafrost in the roadbed at the required depth was developed. The main causes of road failure in permafrost regions were identified. The effect of water accumulated at the base of the roadbed on the temporal variation of the inclined permafrost table depending on the road slope was studied using numerical modeling. Numerical modeling was used to select the key geometric parameters of the design and technological solution controlling the temperature variation of the foundation soils. Regression equations describing the temporal variation of the slope of permafrost table in the roadbed were obtained using the mathematical planning of the experiment.

Icing formation represents a hazardous engineering-geological process that adversely affects infrastructure facilities. To predict icing development and suggest adequate control measures, it is necessary to identify the location of the icing water source and plan the placement of water intake wells. Geophysical methods help solve these tasks. The objective of this study was to investigate the structure of the groundwater discharge zone feeding a hydrogeogenic icing to plan anti-icing measures. The investigations employed ground-penetrating radar (GPR) equipped with an OKO-3 system and a 250 MHz antenna, capacitive-coupled resistivity measurements using VEGA instrument at 16.5 kHz frequency, and electrical resistivity tomography with induced polarization measurements using Skala-64k15 system. GPR data revealed that the seasonal freezing depth within the icing mound reaches 1.8-2.7 m. Signs of groundwater discharge were identified as local anomalies with reduced seasonal freezing depth down to 1.3 m. The study established that the icing mound forms over a seasonal frost heave mound containing an ice core, while the bedrock base shows evidence of a fault zone. Electrical resistivity tomography surveys and 3D modeling of resistivity and normalized chargeability distributions to a depth of 100 m enabled the identification and delineation of branching vertical channels of ascending groundwater filtration. These channels form a group source feeding the icing.

On August 8, 2025, Igor Vladimirovich Klimovsky, a senior researcher at the Melnikov Permafrost Institute, Candidate of Geographical Sciences, Honored Worker of the Economy of the Republic of Sakha (Yakutia), Veteran of Labor, and Honored Veteran of the Siberian Branch of the Russian Academy of Sciences, passed away at the age of 90. He will be remembered as a remarkable permafrost researcher committed to geocryological science, a tireless explorer, and an excellent field worker.