Melnikov Permafrost Institute of the Siberian Branch of the Russian Academy of Science

A brief review of research on variation of thermal resistance of snow cover and formulas to determine the thermal conductivity coefficient of snow are presented. This article aims to establish the regularities of variation in thermal resistance of snow when compressive melioration is applied to the snow cover. A criterion consisting of ratio of initial thermal resistance to the thermal resistance after compression is introduced. Two practically relevant cases, a full and partial compression, whereby the snow density after compression is a constant and a variable respectively, are considered. It is demonstrated that the area where it can be assumed that the snow density after compression is a constant has a low confidence interval and in practical applications it needs to be accounted for that the snow cover is not fully compressed under load. The calculation results are presented in a generalized dimensionless form that includes an indicator of arbitrary exponent in an approximated formula to determine the thermal conductivity coefficient from snow density. It has been established that the type of functional dependence of thermal conductivity coefficient on snow density has a significant influence on the calculation results of the thermal resistance of snow cover. The boundary values of snow compression coefficient within the permissible error level (10 %) were found. For example, for a linear dependence of the thermal conductivity coefficient on density the permissible compression coefficient is no higher than 1.25. For a quadratic dependence, it is 1.11. The results of variant calculations are presented as 2D and 3D charts, which allow quickly assessing the assumptions and conclusions.

In recent years, forest fires have demonstrated an increasing trend in Yakutia, associated with modern global warming and extensive activation of cryogenic processes. In Central Yakutia, an ice complex is widespread, confined to the inter-alas type of terrain. Thawing of the ice component of the soils leads to the development of thermokarst, which is observed in disturbed treeless areas. The general climatic conditions, lithological and geocryological characteristics of the areas for which numerical modeling of the thermal state of soils was performed are described. The thermal state of inter-alas soils in 8 areas after forest fires was modeled during vegetation restoration, taking into account the current trend of increasing air temperature by 0.02о /year. The models were compiled for key periods of change in surface conditions and vegetation: 3, 8, 10 and 25 years after forest fires. It was revealed that in the Pokrovsk, Borogontsy and Berdigestyakh areas, it is possible to reach the depth of thawing of the ice horizon, which is due to high mean annual air temperatures and the spread of sandy loam in the upper part of deposits. And if the vegetation is not restored within the first three years, then presumably cryogenic processes will occur in these areas. In other areas, according to the modeling results, thawing does not reach the ice complex; gradual self-restoration of vegetation should bring geocryological conditions to their original state within 20-25 years. Soil temperatures are expected to rise, which is related to the current general warming of the climate. If the warming trend continues, thawing and soil temperature increases will be more significant and noticeable.

The article is devoted to a strong earthquake that occurred on June 28, 2025 in the north-east of Yakutia, the southern Dmitry Laptev Strait. This event was called the South Anyui earthquake, since it is associated with tectonic manifestations of the South Anyui suture zone. The earthquake source was located at a depth of 10 kilometers, its magnitude was 5.3, with coordinates 72.33°N, 142.14°E. The earthquake parameters were determined using the "Unique Scientific Installation" [Dyagilev, Sdelnikova, 2022]. The epicenter of the earthquake was located on the territory of the Ust-Yansky district, the Republic of Sakha (Yakutia), the Russian Federation. The intensity at the epicenter, according to instrumental data from the GS RAS (http://www.gsras.ru), reached 6–7 points on the MSK-64 scale. The features of the Tastakh trough and the associated magnetic anomaly in the South Anyui suture zone are considered.

Icings, a significant hydrogeological phenomenon in permafrost regions, form when groundwater flows to the surface or through river crevices and freezes under low temperatures. These formations pose serious threats to infrastructure, including roads, railways, and bridges, while also serving as vital freshwater resources. Despite their importance, the mechanisms governing icing formation and the quantitative relationships between groundwater-controlling factors—such as freeze–thaw processes and precipitation—and icing distribution remain poorly understood. This knowledge gap hinders disaster prevention efforts and the sustainable utilization of water resources in cold regions. This study investigates the development patterns and influencing factors of icings in Eruu, a high-latitude permafrost region, using Landsat 4–5 TM, Landsat 7 ETM+, Landsat 8 OLI, and Landsat 9 OLI imagery with a 30 m resolution (2005–2024) and meteorological and geothermal data. By combining NDSI and MDII, the differentiation accuracy of water bodies was improved, and the K-Means clustering algorithm was applied to extract the icing region. The results revealed that the annual icing surface area ranged from 208,800 to 459,000 m2, with a minimum in 2009 and a maximum in 2011. The average annual increase was approximately 4304.5 m2 (p = 0.0255). Icings began freezing in October, radiating outward from the center, and melted by late May or early June. The Pearson correlation analysis showed (1) a strong negative correlation between snowfall and icing area (r = −0.544); (2) a positive correlation between freezing duration and icing area (r = 0.471); and (3) over the study period, annual average temperature and total precipitation exhibited no obvious change trend, with weak positive correlations between icing area and total precipitation (r = 0.290) and annual average temperature (r = 0.248). The observations of icing areas will be further applied to disaster prevention efforts. Additionally, the source of icings is clean and can be extracted for drinking purposes. Therefore, these findings enhance the understanding of icing mechanisms, support the prediction of icing development, and inform disaster prevention and resource management in permafrost regions.

Oxygen-containing functional groups were detected on the surface of diamond nanopowders obtained by grinding natural diamond and detonation synthesis before and after thermal oxidation with atmospheric oxygen using titration, X-ray photoelectron (XPS), and infrared (IR) spectroscopy methods. It was found that, on the surface of natural nanodiamonds after thermal treatment, the content of oxygen-containing groups increases from 26 to 29 μmol/g, and on detonation synthesis nanodiamonds, it increases from 250 to 263 μmol/g. It was found that the content of carboxyl groups increases simultaneously with a decrease in the content of hydroxyl groups in samples of both natural nanodiamond and detonation synthesis nanodiamond. In the initial sample of detonation nanodiamond, the content of lactone groups was 20 μmol/g; after thermal oxidation their content decreased to 5 μmol/g.

In central Sakha (Yakutia) Republic, groundwater icings, primarily formed by intrapermafrost water, are less prone to contamination and serve as a stable freshwater resource. The periodic growth of icings threatens infrastructure such as roads, railways, and bridges in permafrost areas. Therefore, research in this field has become urgently necessary. This study aims to analyze the impacts of various factors on the scale of icing formation using Landsat satellite data, Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GRACE-FO) data, Global Land Data Assimilation System (GLDAS) data, and field observation results. The results showed that the surface area of icings in the study area showed an overall increasing trend from 2002 to 2022, with an average growth rate of 0.06 km2/year. Suprapermafrost water and intrapermafrost water are the main sources of icings in the study area. The total Groundwater Storage Anomaly (GWSA) values from October to April showed a strong correlation with the maximum icing areas. Icings fed by suprapermafrost water were influenced by precipitation in early autumn, while those fed by intrapermafrost water were more affected by talik size and distribution. Climate warming contributed to the degradation of the continuous permafrost covering an area of 166 km2 to discontinuous permafrost, releasing additional groundwater. This may also be one of the reasons for the observed increasing trend in icing areas. This study can provide valuable insights into water resource management and infrastructure construction in permafrost regions.

The history of studying glacial complexes in North-Eastern Siberia goes back more than 150 years. During this period, extensive geological and geomorphological features were obtained, which made it possible to determine the stages, nature and extent of glaciations. At the same time, the lack of direct dating of the glacial relief obtained by geochronological methods does not allow for full-fledged paleogeographic reconstructions. This leads to discussions in both Russian and English literature about the possibility of the existence of glaciation in the mountains of North-Eastern Siberia. In this regard, to determine the size and time of glaciation in the southern part of the Chersky Range, we carried out a complex of geomorphological and geochronological studies, which are part of the international project “Searching for the missing ice sheet in Eastern Siberia”. Because of fieldwork in the Ohandya Ridge, in the Malyk-Sien River valley, three terminal moraine ridges have been identified, reflecting different stages of glaciation. Based on the dating of exposed boulders within three terminal moraine complexes, 22 10Be cosmogenic dates were obtained. The average exposed age for the outer moraine is 120.8±13.7 ka, for the middle one North-Eastern 37.7±4.9 ka and for the internal moraine North-Eastern 13.8±2.2 ka. The age of the terminal moraine complexes testifies to the mountain-valley character of the glaciation of the Chersky Range in the Middle and Late Pleistocene, and emphasizes the trend towards a gradual decrease in the maximum length of glaciers in Northeast Asia. The successive reduction of glaciers from MIS 6 to MIS 2 indicates an increase in the deficit of atmospheric precipitation and a significant cryoaridization of the region. The decreasing trend may be related to the sharply continental conditions observed in the interior of Eurasia and western North America. This trend contrasts with much of the glaciated areas in the Northern Hemisphere, where the maximum area of Late Pleistocene glaciers is reconstructed for LGM time (MIS 2). The obtained datings of the glacial complexes of the Chersky Ridge confirm that at the end of the Middle and Late Pleistocene glaciations here were of a limited nature and there was no single ice cover in the mountains.

The China–Russia crude oil pipeline (CRCOP) operates at a temperature that continuously thaws the surrounding permafrost, leading to secondary periglacial phenomena along the route. However, the evolution and formation mechanisms of these phenomena are still largely unknown. We used multi-temporal airborne light detection and ranging (LiDAR), geophysical, and field observation data to quantify the scale of ponding and icing, capture their dynamic development process, and reveal their development mechanisms. The results show that the average depth of ponding within 5 m on both sides of the pipeline was about 31 cm. The volumes of three icings (A–C) above the pipeline were 133 m3, 440 m3, and 186 m3, respectively. Icing development can be divided into six stages: pipe trench settlement, water accumulation in the pipe trench, ponding pressure caused by water surface freezing, the formation of ice cracks, water overflow, and icing. This study revealed the advantages of airborne LiDAR in monitoring the evolution of periglacial phenomena and provided a new insight on the development mechanisms of the phenomena by combining LiDAR with geophysics and field observation. The results of our study are of great significance for developing disaster countermeasures and ensuring the safe operation of buried pipelines.

Abstract With climate warming and drying, fire activity is increasing in Cajander larch (Larix cajanderi Mayr.) forests underlain by continuous permafrost in northeastern Siberia, and initial post-fire tree demographic processes could unfold to determine long-term forest carbon (C) dynamics through impacts on tree density. Here, we evaluated above- and belowground C pools across 25 even-aged larch stands of varying tree densities that established following a wildfire in ~ 1940 near Cherskiy, Russia. Total C pools increased with increased larch tree density, from ~ 9,000 g C m−2 in low-density stands to ~ 11,000 g C m−2 in high and very high-density stands, with increases most pronounced at tree densities < 1 stem m−2 and driven by increased above- and belowground (that is, coarse roots) and live and dead (that is, woody debris and snags) larch biomass. Total understory vegetation and non-larch coarse root C pools declined with increased tree density due to decreased shrub C pools, but these pools were relatively small compared to larch biomass. Fine root, soil organic matter (OM), and near surface (0–30 cm) mineral soil (MS) C pools varied little with tree density, although soil C pools held most (18–28% in OM and 44–51% in MS) C stored in these stands. Thus, if changing fire regimes promote denser stands, C storage will likely increase, but whether this increase offsets C lost during fires remains unknown. Our findings highlight how post-fire tree demographic processes impact C pool distribution and stability in larch forests of Siberian permafrost regions.