Vol. XXVIII, No. 4 (July – August 2024)
Full issue:   EC_4_2024_engl_opt.pdf

CONTENTS

GEOCRYOLOGICAL MONITORING AND FORECAST

  • Berdnikov N.M. Cartographic visualization of the expected change in the southern permafrost limit in Western Siberia
    Abstract
    In the era of modern climate change, permafrost degradation takes place in Western Siberia. It is manifested by an increase in permafrost temperature, a decrease in the permafrost area, and a reduction in the thickness of frozen layers. To establish the rate of reduction in the area of permafrost distribution, a cartographic model predicting the change in the position of its southern boundary by the middle of the 21st century was created. Taking into account temperature, ice content, rock composition, and structure of the section, southern areas of permafrost in Western Siberia were ranked according to the order of the long-term thawing of the upper 10-meter-thick permafrost section. It was found that the expected change in the southern permafrost limit in Western Siberia will be uneven and dependent on local conditions related to the cryolithogenic characteristics of the landscape.
    Keywords
    southern permafrost limit, cartographic model, climate change, permafrost degradation from the surface, annual temperature fluctuations layer

PROPERTIES OF FROZEN GROUND AND ICE

  • Neradovskii L.G. Verification of the accuracy of the model for predicting strength of sedimentary rocks of Southern Yakutia based on geometric electromagnetic induction sounding
    Abstract
    This article discusses the results of retrospective verification of the strength prediction model for saturated rocks of southern Yakutia. The model was developed for the geotechnical conditions of the city of Neryungri. The input data for the model consisted of the decay rate coefficients of the harmonic field of a vertical magnetic dipole measured at a 1.125 MHz frequency using the geometric electromagnetic induction sounding method. The error of model predictions was close to the allowable error of ±20% for average laboratory estimates of rock sample strength and ranged from ±16.8 to ±33.5% for different site conditions with a probability of about 70%. The total error of the model at this probability is 27.2% with maximum outliers overestimating the laboratory strength of weak rocks by 120.5% or underestimating the strength of strong rocks by 86.8%. The model predictions were more accurate (errors of 22.8 and 21.9%) for the rock masses composed predominantly of moderately strong (15–50 MPa) and strong (50–120 MPa) rocks. The statistical results indicate that the model is regionally representative and can be applied in the areas of warm and cold permafrost sedimentary rocks of southern Yakutia for rapid, cost-effective terrain evaluation by rock strength.
    Keywords
    model for Neryungri City, sedimentary rocks, rock mass and laboratory samples, saturated rock strength, geometric sounding, remote electromagnetic inductive sounding, verification, error

SURFACE AND GROUND WATERS IN TERRESTRIAL PERMAFROST REGION

  • Fedorov M.A., Fedorov A.A., Pavlova N.A. Subpermafrost groundwater in the Northeastern part of the Lena–Amga interfluve
    Abstract
    The purpose of this work was to specify the hydrogeological conditions in the poorly studied north-eastern part of the Lena–Amga interfluve. We analyzed archival (1965–1995) and published data on subpermafrost waters and permafrost thickness in the Churapcha and Tattinsky districts of the Republic of Sakha (Yakutia), including new field studies (2009–2022). The research was based on the data from 19 groundwater exploration boreholes, 450 to 650 m in depth. It is shown that the Jurassic and Middle Cambrian aquifer complexes differ in piezometric pressures and chemical composition. Based on the new information, it is suggested to shift the estimated boundary of fissured formation groundwater occurrence in terrigenous carbonate sediments northwards by 50–80 km. A zone with distinct hydrogeological conditions near the Tatta–Tompo fault was identified. Presumably the fault was formed under conditions of horizontal compression, which resulted in compaction of rocks, which reduced permeability along the fault, and increased freezing intensity in strata with low water content during periods of decreased global temperatures.
    Keywords
    groundwater, Middle-Cambrian aquifer system, Jurassic aquifer system, Tatta–Tompo fault, hydrostatic level, chemical composition

GASES AND GAS HYDRATES IN THE EARTH’S CRYOSPHERE

  • Istomin V.A., Sergeeva D.V., Chuvilin E.M., Bukhanov B.A., Sokolova N.S. Method of rapid estimation of the effect of the hydrate-forming gas pressure on nonclathrated water content in soils
    Abstract
    Natural gas hydrates exist in porous media at high pressure and low temperature, including permafrost. The development of express methods for calculating hydrate phase equilibria in soils and sediments, including the equilibrium content of nonclathrated water, i.e., the pore water, which is in equilibrium with hydrate and hydrate-forming gas under given thermobaric conditions, is of special interest in the study of natural hydrates. Nonclathrated water is similar to unfrozen water in frozen soils. The current study covers thermodynamic relationships for calculating nonclathrated water content in soil under certain thermobaric conditions on the basis of experimental data of pore water activity and soil water content. It is shown that at a fixed temperature the nonclathrated water content sharply decreases according to a power law during an increase in gas pressure. The results of thermodynamic calculation are in agreement with direct measurements of nonclathrated water in soil systems using the contact method. Thus, at temperatures below 0°C, the content of nonclathrated water in kaolinite clay and in sandy clayey soils decreases by more than two times with an increase in methane pressure from 2.3 to 11 MPa. The obtained relationships allow us to recalculate the nonclathrated water content upon transition from one hydrate-forming gas to another, as well as calculate nonclathrated water content using the unfrozen water content curve at different temperatures. The developed thermodynamic approach can be applied to various hydrate-forming gases and their mixtures.
    Keywords
    gas hydrates, sediments, pore water, phase equilibria, nonclathrated water, unfrozen water, ice, thermodynamic calculations

SNOW COVER AND GLACIERS

  • Sosnovsky A.V., Osokin N.I. Snow storage in forests and fields on plain territories of Russia under modern climate
    Abstract
    Climate change affects the parameters of snow cover, including the distribution of snow storage for Russia territory plains in forests and fields. The comparison of the average long-term maximum snow storage in forests and fields for different climatic periods is carried out. It was found that for Russia flat land, the average maximum snow storage in forests for the periods 1966–1990, 1981–2010 and 1991–2020 were 132, 129 and 125 mm in water equivalent, respectively. Whereas in fields – 115, 120 and 120 mm, respectively. The average value of snow storage in the field for the current climatic period 1991–2020 increased by 4% compared to the period 1966–1990 and decreased in the forest by 6%. Snow storage in forests and in fields for the period 2001–2010 amounted to 127 and 123 mm, and for the period 2011–2020 snow storage in the forest and in the field decreased to 121 and 120 mm, respectively. The ratio of snow storage in forest to its value in fields – the snow accumulation coefficient for 1966–1990, 1981–2010 and 1991–2020 has been constantly decreasing and amounted to 1.16; 1.08 and 1.05, respectively. Maps of the distribution of snow storage and the coefficient of snow accumulation for Russia flat land for different climatic periods have been constructed. The tendency of leveling the maximum snow storage in forests and fields under the modern climate (1991–2020) has been confirmed.
    Keywords
    snow storage, field, forest, climatic periods

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