Seasonal soil freezing in the Middle Ob region on the territory of Khanty-Mansi Autonomous Okrug - Yugra
S.E. KORKIN1,2, E.A. KORKINA1, V.A. ISYPOV1
1Nizhnevartovsk State University, Nizhnevartovsk, Russia
2Institute of Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences, Yekaterinburg, Russia
Keywords: seasonal permafrost, snow cover, temperature, climatic factors, soil freezing, Fibric Histosols
Abstract
Presented are the results from studying the seasonal soil freezing dynamics during 2009-2023 in a section of the Ob River valley in Khanty-Mansi Autonomous Okrug-Yugra (the territory of the Middle Ob region). In this study area there occur alluvial sod-gley soils in the floodplain on the pine-sphagnum bog peaty upland (oligotrophic soils), peaty-gley soils in the pine swamp forest, and illuvial-iron podzols under the mixed birch-aspen-Siberian stone pine stands. Data from neighboring sites located to the north and south of the main fixed station are used for comparative characterization. The purpose of this study is to reveal the seasonal freezing dynamics in the Middle Ob region. The objectives of the study are focused on identifying the long-term seasonal freezing dynamics in the southern permafrost zone. The research methods are based on field measurements using soil pits and snow measurements in the second half of March and the first half of April. The results of measurements from 2009 to 2023 revealed a decrease in the depth of soil freezing starting from the year 2015. It was found that the average annual temperature of the peat oligotrophic soils is 4.49 °С. An increase in the mean annual temperature at a depth of 0.20 m by 1.16-1.45 °С was noted. The mean annual temperature for illuvial-iron podzols at a depth of 0.20 m is 3.87 °C. The mean annual temperature gradient varied from 0.35 to 1.23 °C. The mean annual temperature for alluvial sod-gley soils during the study period was 5.23 °C. The average annual temperature gradient ranged from 0.42 to 1.12 °С. The results of snow survey allowed us to calculate the water equivalent of snow cover for the 15-year period. The average annual snow cover height was 76 cm. The water equivalent of the snow cover was high: 259 mm in 2015 and 232 mm in 2020. The data obtained in the course of the study show that, within the key area, freezing depends on the integrating landscape-forming geocomponents and reflects the manifestation of the global climatic trend with local variations.
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