Home – Home – Jornals – Earth’s Cryosphere 2024 number 5

The results of studies of the Ice Complex, lacustrine, and lacustrine-alluvial sediments from the Mamontova Gora section performed in 2022-2023 are analyzed. Optically stimulated luminescence dating indicates that the formation of the lacustrine-alluvial sands of the Elga Group ended 250-242 ka ago, at the end of cold MIS 8, while the overlying lacustrine silts accumulated until 138-126 ka ago corresponding to the late cold MIS 6 - early warm MIS 5e. The average isotopic composition of the Yedoma Ice Complex (MIS 3) syngenetic wedge ice is -(31 ± 2)‰ for δ¹⁸O, -(239 ± 15)‰ for δD, and (8 ± 2)‰ for d_exc. For the first time, we quantify the isotopic composition of the Yedoma Ice Complex textural ice with the average values of -(26 ± 2)‰ for δ¹⁸O, -(201 ± 17)‰ for δD, and (10 ± 4)‰ for d_exc. The formation of lacustrine and lacustrine-alluvial sequences during MIS 7 and MIS 5e was fostered by warmer and likely longer thaw periods and associated permafrost thaw. The degree of warming remains to be estimated for this region.

A classification of periglacial lakes that formed in Svalbard after the Little Ice Age due to the reduction of glaciation is presented. The classification is based on three morphological features: the position of the lake relative to the boundaries of the glacier and the terminal moraine, contact with the glacier, and the damming condition. Combinations of these features allow us to distinguish five types of lakes. Based on the Norwegian Polar Institute cartographic service as of 2008-2012, 705 periglacial lakes of the archipelago were analyzed. Among them, glacier-dammed lakes make up 24%; moraine-dammed lakes, 22%; lakes in contact with the glacier front, 17%; thermokarst lakes over the moraine, 27%; and lakes in contact with the terminal moraine located beyond it, 10%. Dammed lakes and lakes in contact with glaciers compose about 90% of the total area of periglacial lakes in Svalbard. They are actively forming at present due to the destruction of ice banks and moraine ridges. Despite the differences in the relief, type of glaciation, climate, and rate of glaciation reduction in different parts of the archipelago, the ratios between different types of periglacial lakes are similar. This attests to their common genesis and similar features of the moraine landscape. Noticeable differences appear in the ratio of moraine-dammed lakes and lakes in contact with mountain glaciers and cover glaciers. It is likely that during the further deglaciation of the archipelago, the distribution of these types of lakes will be preserved, which makes it possible to assess lake resources and identify potentially dangerous objects and objects of climate monitoring.

This paper provides a detailed review of the methods of active temperature stabilization of frozen soils with an emphasis on stabilization systems with a horizontal evaporator. The experience of Russian and foreign authors in the field of single seasonal cooling devices is presented. The range of seasonal cooling devices applied in Russia and the objects, at which they are installed, are considered. The mechanism of action of both single cooling devices and temperature stabilization systems with a horizontal evaporator is shown. The paper also presents a new experimental installation for thermal stabilization of frozen ground with a horizontal evaporator, on which a number of experiments have been conducted to study refrigerant flows in the circulation circuit of the proposed system under different thermal conditions affecting the evaporator. A description of a full-scale stand is given, and the principle of supplying positive temperature to the evaporator in order to simulate heat removal from the ground and its further dissipation into the atmosphere is described. At present, systems of this type usually use ammonia as a refrigerant; in the proposed system, carbon dioxide is used. It has been shown that the capacity of the installation based on carbon dioxide can be significantly higher than that based on ammonia. The study results make it possible to optimize the configuration of the ground temperature stabilization system with a horizontal evaporator for particular construction sites. The efficiency of the developed system is much better compared to the analogues, which significantly reduces the risk of thawing of frozen ground at operational sites. This is especially relevant at hazardous production facilities working with harmful substances, the ingress of which into the soil imposes a significant ecological trace.

The study and prediction of subsea permafrost conditions hold profound significance in the context of global climate change, the formation of gas hydrates, and the assessment of natural hazards arising from the permafrost thawing. This study presents a forecast of relict subsea permafrost distribution across the Eurasian Arctic shelf through the resolution of a one-dimensional, non-stationary Stefan problem using finite difference methods, facilitated by contemporary software tools and libraries. The mathematical description of the model is presented. Particular attention is paid to the boundary conditions of the model and their synthesis. Calculations take into account the climate clustering of the expansive Eurasian shelf, considering zonal variations in both near-surface air temperature and the temperature and salinity of subsea waters. For the first time, model estimates of the position of the upper boundary of subsea permafrost are presented, and its position is compared with drilling data. Analysis of the influence of boundary conditions on the simulation results and comparison of our results with seismoacoustic and drilling data confirm the good quality of the model. The evolution of subsea relict permafrost in time is represented by a set of three maps for the Late Pleistocene-Holocene time spans. As a result, a high-resolution global two-dimensional map of the thickness of underwater permafrost on the Eurasian shelf was created. Detailed modelling and forecast mapping of the distribution of permafrost table was carried out in well-studied areas. According to our forecasts, a wide distribution of subsea relict permafrost is predicted throughout the Eurasian Arctic shelf. The greatest thickness of relict frozen deposits is confined to the littoral zone of the Laptev and East Siberian seas, as well as the offshore of the New Siberian Islands. In the Pechora and Chukchi seas, mostly poorly developed, close to complete degradation, relict subsea permafrost is predicted.

To determine the current state of the permafrost in the Yamalo-Nenets Autonomous Okrug and assess its transformation in connection with modern climate changes, transient electromagnetic (TEM) sounding was performed at ten sites along the submeridional profile from the Siberian Uvaly Hills in the south to the Pur-Taz Lowland in the north with a step of about 50 km. An interpretation of geoelectric models was carried out and the results of drilling surveys of permafrost were compared with those provided by the Arctic Research Center from its archive. As a result of the interpretation of geoelectric sections, modern and relict permafrost strata and closed taliks were identified. It was found that the modern base of permafrost lies at depths from 50 to 130 m. A comparison of the results of modern TEM surveys with archival reference geocryological sections did not show significant differences in the position of geocryological boundaries. However, it is necessary to note the significant distance between the TEM sites, as well as, often, considerable distances between them and reference boreholes. The greatest differences between the modern and archival data are noted in the northern part of the profile, which is probably due to the increased salinity of the rocks at the TEM survey sites.