Vol 64, No 2 (2024)
Glaciers and ice sheets
Changes in water regime in the high-mountain region of the Terek River (North Caucasus) in connection with climate change and degradation of glaciation
Abstract
In this study, we adapted the ECOMAG model of the runoff formation for analysis of the Terek River basin using comprehensive hydrometeorological information as well as data on soils, landscape, and glaciation. To take account of regional characteristics of the glaciation, the additional ice module was used with the model. This improvement has resulted in a satisfactory agreement between the modeled runoff hydrographs and the observed ones. In our simulations we used the updated glacier cover predictions from the- global glaciological model GloGEMflowdebris together with regional climate projections from the CORDEX experiment to determine possible future changes in the Terek River flow in the 21st century. The results show that the runoff will change between −2% and +5% according to the RCP2.6 scenario, and from −8% to +14% in the RCP8.5 scenario. The directedness of the runoff changes in particular subbasins of the River will essentially depend on the altitude position of the snow and glacier feeding zones, that is responsible for the intensity of their degradation. Thus, in the RCP8.5 scenario, the flow of the Chegem River will begin to decrease significantly in the second half of the 21st century. In contrast, the predicted increasing of the runoff in Malka and Baksan rivers, which are primarily fed by meltwater from glaciers and snow on Elbrus and other high-mountain zones, is expected to be continued until the end of the century. But this increase may be caused only by a growth of a part of the snowmelt feeding due to greater winter precipitation. The model estimates confirm the present-day observed trends within the intra-annual runoff distribution, demonstrating the earlier start of the spring flood, a decrease in summer runoff volumes and then its increase in the autumn months. The results of the research may be used for more efficient management of water resources in the North Caucasus in the future, including electricity generation and water supply.
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The outburst of dammed lake Maashey (North-Chuya ridge, Central Altai)
Abstract
The dammed lakes are widespread in mountainous areas and usually occur when river flow is blocked by landslides, rock glaciers, etc. Among such lakes, the most dangerous are those located in the periglacial zone and blocked by rock glaciers. Continued deglaciation of mountainous areas under changing climate conditions contributes to accumulation of large volumes of melt water in lakes, which may increase pressure on the dam, cause its failure and subsequent outburst flood. In this article we describe the development of such a lake before its outburst and the process of its outburst. The object of study was Maashei Lake (North Chuya Ridge, Central Altai) located in the zone of mountain glaciation and dammed by a rock glacier, where the lake outburst occurred in July 2012. The lake area before the outburst was 259 × 103 m2 and water volume 1.21 × 106 m3. As a result of the outburst, the lake was completely drained. We analyzed the published works on Lake Maashei, materials of our own field studies in the lake basin combined with remote sensing data. We hypothesized that the mechanism of the outburst occurred in 2012 was caused by the water erosion of the filtration channel in the dam body. The mechanism of this outburst was numerically simulated using the method presented in this article. The modeling allowed to reproduce the outburst flood hydrograph, to estimate such characteristics as maximum water discharge, volume of the outburst flood, water flow velocities and the size of the formed breach. Estimated maximum discharge was 694 m3s−1, flow velocities varied from 0.2 to 5-7 m s−1, and the outburst flood period was about 5.5 hours. The breach was formed to the full height of the dam (10 m). Its calculated morphometric characteristics were as follows: average width 47.5 m (measured 41.5 m), скоss-section area 476 m2 (measured 415 m2). The discrepancy between the modeled and measured values was about 15%.
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About the ice-rock collapse from the northern slope of Mt. Dykhtau on August 12, 2023 and the potential threat of collapse from the slope of Mt. Dzhangitau (Cherek-Bezengiysky River basin, Central Caucasus)
Abstract
The causes and consequences of the ice-rock fall that occurred in 2023 on the Mount Dykhtau (Side ridge of the Greater Caucasus) are analyzed. This happened in the early morning of August 12, 2023 on the northern slope of Mt. Dykhtau (5.204.7 m a.s.l.) in the upper reaches of the Mizhirgi River valley of the Cherek Bezengiysky River basin at the altitude of about 4.400 m. The analysis of Sentinel-2 and Landsat-7 ETM+ satellite images of different times made possible to reveal the place where a block of ice had fallen from the hanging glacier, and to determine the area affected by this ice-rock block which volume was estimated as close to 0.9-1.0 million m3 and a distance of the runout about 2.3 km. As a result of the collapse, a group of tourists were injured, one of whom died. Investigation of the dynamics of the collapse site for the period 2015–2023 showed that earlier in the period September 3 – November 12, 2015 a crack formed on the same hanging glacier massif, which continued to grow until January 2016. This was followed by several ice-rock falls, the largest of which happened in the period April 10 – June 19, 2016. In total, all collapses of 2016 were comparable in volume to the collapse of 2023. By this time, the hanging glacier had been fully restored and occupied the same position it had in 2015. We next investigated a part of the slope of the Dzhangitau Zapadnaya mountain (5059 m a.s.l.) on the Bezengi Wall massif, on the hanging glacier of which the formation of a crack with a length of about 400 m was revealed in the summer of 2023. By September, the crack width had increased to 40 m. Leyer on, the crack became stable. But in the period of September ‒ December a certain surge of the glacier at the foot of Dzhangitau Zapadnaya mountain was revealed at a speed of about 1 m per day with the formation of a prominent frontal bank overlying the Bezengi Glacier. This research confirmed the activation of the landslide processes in the high-altitude zone and showed the need for continuous monitoring based on the analysis of satellite images for the timely revealing areas with a potential threat of any ice-rock falls and warning about the danger.
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Characteristics of the hydrological regime of the periglacial moraine lakes in the Altai
Abstract
In the last decade glaciers of Inner Asia have been shrinking with acceleration, and the number of glacial lakes has been growing significantly, including those with a high probability of outburst and high-water discharge. The hydrological regime of lakes in the Altai is understudied in comparison with lakes in other high mountain countries. The article is based on our extensive field material on hydrological and morphometric characteristics of moraine lakes collected in the Russian and Mongolian parts of the Altai Mountains and combined with the Earth remote sensing data. We have proposed detailed indicators (criteria) of transgressive, regressive and post-regressive stages of lake development. It allows allow to determine at a qualitative level at what stage a lake is at and to assess its further development. The characteristics of hydrological regime of Altai lakes at different stages of development are described for the first time. Based on the criteria proposed, the classification of glacial and moraine lakes in the Altai high mountains was carried out. It shows that at present most of the lakes are in the transgressive stage. Over the last 22 years, the number of lakes has increased significantly: on the territory of the North Chuya Ridge – from 28 to 60, on the South Chuya Ridge – from 39 to 73, on the Katun Ridge – from 57 to 89, on the territory of the Tavan-Bogdo-Ola massif – from 11 to 19, and on the territory of the Mongun-Taiga massif – from 8 to 11 lakes.
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Snow cover and avalanches
Areas of maximum intensity of avalanche formation in the Greater Caucasus associated with large anomalies of temperature and humidity regime
Abstract
The purpose of this paper is to substantiate the geographical boundaries of areas which are distinguished in the Greater Caucasus by the intensity of avalanche formation at the large-scale hydrometeorological anomalies and can be classified as “epicentres” of the avalanche activity. For the period of snow avalanche observations in the Caucasus in the 20th century, the Nature did twice demonstrate “experiments” in the winters of 1975/76 and 1986/87, during which especially intensive releases of avalanches occurred in the same areas of the southern macro-slope of the Central Caucasus. This work is an effort to answer the question ‒ why the main impacts of the snow disasters occurred within the boundaries of the same territories. The results of the analysis show that the highest intensity of avalanche activity is observed in those areas where three factors of avalanche formation are simultaneously realized: a big number of large avalanche catchments, including ancient glacial cirque zones (corries); high snowiness; types of snow favourable for the mass releases of especially strong avalanches. In the Caucasus, these criteria are met by the usually identified watershed zone of the Main Caucasus Range and, as the analysis showed, the territory of mountainous Georgia in the Inguri River basin (with tributaries of the Nenskra, Nakra, Mestia-Chala, Dolra, Mulkhura rivers), as well as the upper reaches of the river Kodori (Abkhazia). According to the USSR Glacier Inventory (1986), up to 80% of the corrie relief forms of the southern macro-slope of the Caucasus are concentrated in the basins of the Inguri and Kodori rivers, many of which are centres of origin of especially strong avalanches. The high snowiness of this territory, as compared to neighbouring areas, is conditioned by the influence of the orography and the climate effect, that is seen on the map of the solid precipitation distribution in the Atlas of Snow and Ice Resources of the World (1997). Only in this sector of the Greater Caucasus is there a kind of “peninsula” of high snowfall extending for tens of kilometers towards the moisture-bearing airflows from the Black Sea. Temperature conditions in the zone of increased snow accumulation are the factor contributing to the avalanche formation, which is manifested in its structural, textural and strength properties.
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Mechanism of ion migration from the substrate material into snow cover at the end of the cold period
Abstract
Earlier, it was established that maximum mineralization of the contact layer of snow occurs in spring at the interface with substrates (soil or ice). This study analyzes the temperature and moisture conditions during this period at the interface of the contact layer of snow with substrates by examining frozen sand blocks saturated with a solution containing complex gold ions, or blocks filled with polystyrene containing ions of molybdenum, copper, etc. It is assumed that the migration of ions from the underlying substrate into the contact layer of snow cover in spring occurs along quasi-liquid films on the surface of snow crystals, the thickness of which exceeds the equilibrium one. Migration becomes noticeable when the temperature at the snow–substrate contact reaches −13 °С and above. The appearance of quasi-liquid films on the surface of snow particles under variable temperature and moisture conditions is possible due to the condensation of water vapor, which during the day, with general heating of the system, can enter the contact layer of snow both from above and below. With an increase in snow density in the spring, the mineralization of the near-contact layer of snow cover increases. At the same time, linear relationships were revealed between the content of substrate components migrating into the near-contact layer of snow and the gradient of water vapor density in it. The reliability of the approximation of these dependencies for the gold thiosulfate complex is 0.98; for copper ions – 0.52; for hydrogen ions – 0.88; for sodium ions – 0.69, for chloride anions – 0.89. The results of the study substantiate the increased efficiency of geochemical prospecting for mineral deposits using snow cover in the spring.
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The snow depth and its dynamics on the continental part of the Russian Arctic under conditions of the present-day climate
Abstract
Based on the data of route snow surveys for the period 1966–2020, the comparison of the average long-term maximum depths of snow cover, the depths of snow cover for individual months and the dynamics of snow accumulation (the ratio of the depths of snow cover to the maximum value) on the continental part of the Russian Arctic for two representative periods (1966–1990 and 1991–2020) was made. Maps of snow cover depths and snow accumulation dynamics have been constructed for both periods. These maps made possible to analyze influence of the climatic changes on the depths of snow cover and the dynamics of snow accumulation.
A comparison of these values for the first (1991–2020) period with the same of the second one showed that in October–November in the European part of the Russian Arctic, the snow depths decreased by an average of 22% (first period) and 8% (second period), and in some areas the decrease reached 70 and 20%. In the Arctic part of Western Siberia, these characteristics of snow cover increased. Growth of snow cover depths in November/January/March averaged as 11/20/23%, and in some areas it exceeded 40%. The dynamics of snow accumulation in the Arctic for the whole period 1991–2020 averages 18/37%, in October/November, and 71/91% in January/March. In the European part of the Arctic, these values are smaller: 13/29% and 68/90%, respectively. The dynamics of snow accumulation in the west and in the center of the European Arctic territory by the end of the autumn period does not reach 30%, while in the Arctic part of Siberia this mainly exceeds 50%. In October/November 1991–2020, the dynamics of snow accumulation decreased in several regions of the European Arctic and the Arctic part of Western Siberia as compared to 1966–1990. On average over the entire territory of the Arctic, the decrease in the dynamics of snow accumulation compared to 1966–1990 amounted to 13/4% in October/November, and 3/1% in January/March.
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On the problem of estimating the snowiness of winters by different methods by the example of the Yuzhno-Sakhalinsk city
Abstract
The problem of estimating a snowiness (a snow coverage) of a territory is considered by many authors, but still nowadays no common approach to its solution is reached. Different authors use different characteristics in their works for estimating the winter snowiness. In this work the snowiness of winters was estimated using different parameters to determine the most representative one. The area ща study is the Yuzhno-Sakhalinsk urban district. The data for the past 36 years (1986–2022) were used to determine the types of the winter snowiness in this district. The following nine methods have been applied: the maximum winter snow reserve; by the amount of solid precipitation; by the average winter thickness of snow cover from the weather station and by snow survey; by the average greatest ten-day thickness of snow cover; by the amount of precipitation in the form of snow; the method of N.N. Galakhov; the Schultz coefficient; and the maximum winter snow cover thickness. The results obtained are very contradictory. Thus, the types of snowiness completely coincided in only 17% of winters; while in 58% of winters the types of snowiness coincided by 2/3 of the above indicators. Estimation of snowiness using various parameters gives closer results when using data on snow reserve at the beginning of snowmelt and the average winter thickness of snow cover (coincidence in 78% of cases). The reason is that a major part of the above methods uses the values of only one parameter. But given that snowiness is a complex indicator, it would be reasonable to consider all possible parameters at the same time. It is impossible to develop a unified approach to estimating winter snowiness, since the parameters chosen for this problem depend on the goal of the determination. It would also be worthwhile to select a methodology for estimating winter snowiness depending on the tasks set, and on the availability and reliability of the initial meteorological data for the analysis. Such work is also complicated by the insufficient volume of meteorological data, as well as due to gaps in them.
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Ionic composition of snow cover on the territory of Siberia and the Far East
Abstract
Long-term (from 2007 to 2022) observations of the dynamics of acidity, mineralization and ionic composition of snow cover in remote mountainous and lowland landscapes of Northern Asia were carried out. As a result, spatiotemporal changes in the molar concentration of basic (Ca2+, Mg2+, HCO3-, Cl- and SO42-) and nitrogen-containing (NH4+, NO3- and NO2-) ions were analyzed. It turned out that during the entire observation period, bicarbonate ions prevailed in all monitoring regions, even near the sea coasts, where there is an intensive intake of sulfate and chloride ions into the atmosphere. Until 2012, the molar concentration of these three anions was characterized by higher values, which decreased 3–8 times in subsequent years, this is especially noticeable for bicarbonate ions and to a lesser extent for chloride ions. The molar concentration of nitrogen-containing ions in the snow cover of Northern Asia was at a low level (especially nitrite ions). Ammonium ions were predominant throughout the observation period (especially in mountainous landscapes) and only in some years – nitrate ions.
262-272
Experimental determination of the coefficient of viscosity of the dry snow
Abstract
Snow compaction is a natural process in the evolution of any snow cover, and this obviously changes the physical and mechanical properties of a snow thickness. The quantitative estimate of this process is a coefficient of the snow viscosity, which is linearly related to the rate of the snow cover deformation The technique for preparation and testing of samples with the fine-grain snow under condition of uniaxial compression at negative temperatures is described. It was determined that values of the snow viscosity coefficient fall within the range from 0.10 to 0.30 g/cm³ for three temperature intervals. The viscosity coefficient of the fine-grain snow varies from 10⁸ до 10¹⁰ Па. The data obtained made possible to find the limits of variability of this coefficient for winter conditions on the Russian plain. A dependence of the viscosity coefficient on the snow density and temperature is proposed, and it describes the series of the above shown experimental data. It is shown that influence of changes in the viscosity coefficient of fine-grain snow on the snow properties depending on its density are comparable in scale to the influence of the temperature. The result may be useful for modeling the evolution of snow cover.
273-280
Sea, river and lake ices
Long-term variability of ice regime characteristics in river mouth areas of the western coast of the White Sea on the background of climatic changes
Abstract
The paper presents results of the comprehensive study of the long-term variability of the main elements of the ice regime for the period 1955–2020 in mouth areas of the rivers Gridina, Kuzema, Pongoma, Kem, Shuya, Nizhny Vyg, Suma, Nyukhcha and Maloshuika flowing into the White Sea on its western coast (Republic of Karelia, Arkhangelsk region). The average daily air temperatureы in sites of the State observation network of Roshydromet – marine hydrometeorological coastal stations Gridino, Kem and Onega - were used as initial information for this work. Information about the main characteristics of the ice regime (times of coming of characteristic dates of ice phenomena) of the rivers was presented by data from nine hydrological posts. The mean values of characteristics of the ice regime (average statistical dates and durations of the ice regime phases) of the rivers under consideration (except those regulated by the cascade of hydroelectric power stations). were calculated. Statistical analysis of time series of the mean air temperatures obtained for the cold season on the western coast of the White Sea and the duration of periods with ice phenomena on the above rivers made possible to reveal two quasi-homogeneous periods with a turning point in 1990. This analysis shows that the temperature background in years 1991–2020 is significantly higher (by 1.4 °C) than the similar one in 1956–1990, and at the same time the average duration of ice phenomena decreased to almost two weeks (shorter by 11 days). The regression analysis allowed finding the presence of a statistically significant negative trend in the duration of ice phenomena for the whole period (1956–2020), which is −3.3 days/10 years. At the same time, the shortening of the duration of the periods with ice phenomena is due equally to both a shift in the time of the beginning of the stable ice formations towards later dates (1.6 days/10 years), and the earlier dates of the ice phenomena end (−1.7 days/10 years).
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Express Information
Ice drilling on Princess Elizabeth Land (East Antarctica) aimed to study bedrock and Late Quaternary paleoclimate
Abstract
Targeted bedrock sampling was carried out on Princess Elizabeth Land (30 km south of the coast, at 69.585591° S; 76.385165° E) by drilling through 545 m thick ice. The borehole was drilled using a new, modified version of the cable-suspended Ice and Bedrock Electromechanical Drill (IBED) designed by the Jilin University (China) and under a joint scientific project between VNIIOkeangeologia, Jilin University and China University of Geosciences (Beijing). The drill site is located on the axis of a high-amplitude linear magnetic anomaly that runs parallel to the coast for more than 500 km from Princess Elizabeth Land to Mac. Robertson Land. In the next Antarctic season, borehole geophysical logging will be conducted including temperature measurements for geothermal heat flux calculations.
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