Ice and Snow (E-Journal) / Лёд и Снег
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Формирование ледяной плотины в низовьях рек Мезень и Кулой с 1983 по 2020 г.
Get PDFThe features of ice cover formation within the macro-tidal estuaries of the Mezen River and the Kuloy River are considered. The investigated rivers flow into the Mezen Bay of the White Sea. The main sources of information for the ice monitoring were the high spatial resolution images from the satellites Landsat 5‑8 and Sentinel 1.2 with addition of medium spatial resolution images of MODIS/Terra and VIIRS/SuomiNPP. Every year, zones of continuous hummocks and ice dams are formed in the estuaries, which exert influence upon characteristics of the tidal waves. The fast ice and drifting ice areas are observed below the ice dam. Above the dam, amplitude the tidal fluctuations in the water level is reduced by 3–4 times. According to the data for the period 2017–2020, the area of relatively smooth ice cover is located at the distance of 48–49 km above the mouth of the Mezen River and 40–42 km above the same of the Kuloy River. Advancing of the ice edge to the mouth is accompanied by the formation of hummocky ice bridges, the position of which is confined to the narrowing and sharp turns of the channel. According to satellite images, it is established that the ice dam changes its position from year to year. In the period from 1983 to 2020, on the Mezen River, the ice dam was located at a distance of 21.0 to 30.5 km from the mouth, and on the Kuloy – from 13.7 to 27.5 km above the mouth. The position of the ice dam is weather dependent. In severe winters, the dam is located closer to the mouth gauge line. Snow, falling in November and December on areas of open water, delays advancing of the ice edge to the mouth. For Mezen, the relation between the position of the ice dam and three following predictors had been obtained: the sum of precipitation for November and December at the air temperature below –5 °C, the sum of air temperatures below –5 °C for January and March, and the sum of positive air temperatures for February. The proposed dependence made it possible to restore the positions of the ice dam for the years which were not provided with satellite data. These are 1994 and 1999.На основе данных космических снимков оптического и радиолокационного диапазонов рассмотрены особенности формирования ледяного покрова в пределах макроприливных устьевых участков рек Мезень и Кулой. Ежегодно в исследуемых эстуариях образуются зона сплошных торосов и ледяная плотина, влияющие на характеристики приливной волны. С 1983 по 2020 г. створ ледяной плотины на Мезени располагался на расстоянии от 21,0 до 30,5 км от устья, на Кулое – от 13,7 до 27,5 км от устья. Формирование ледяной плотины и её разрушение происходят с остановками в створах, приуроченных к сужениям и крутым поворотам русла. Показано, что в ноябре и декабре твёрдые осадки значимо задерживают продвижение кромки льда
Метеорологические условия экстремального лавинообразования в горах Кавказа по данным наблюдений и реанализов
Get PDFThe possibility of using the data of modern ERA-Interim, CFSR and NCEP-NCAR re-analyses to assess an avalanche danger in the mountains of the North Caucasus is considered. Previously, the mean seasonal values of the surface air temperature and seasonal precipitation amounts obtained from the reanalysis archives were compared with the data of meteorological stations. The mean temperature of the cold period (November–March) was best reproduced by the ERA-Interim reanalysis: the correlation coefficients amounted to 0.8–0.9, and the average deviation from the station data ±1.7 °C. The accuracy of measurements of precipitation is lower, but the magnitude of the errors does not exceed the limits of inter-seasonal variability. To estimate the avalanche hazard, a correlation matrix was used based on the relationship of the avalanche hazard indicator with the standard deviations of seasonal values of temperature and precipitation. The ERA-Interim reanalysis reproduces the avalanche danger in the North Caucasus most adequately (71% of coincidences with the actually observed events). Synoptic processes which may promote formation of catastrophic avalanches in the North Caucasus were also determined. The most typical situation is the position of a high-level cyclone over the Eastern Europe, accompanied by the invasion of cold air masses from Scandinavia that activates cyclogenesis in the Mediterranean. It was found that the extreme avalanche hazards occurred at negative anomalies of mean seasonal air temperature near the ground and in the middle troposphere (about 1.5–2 °C) when the integral water content of the atmosphere was close to the norm.Рассмотрена возможность использования данных современных реанализов ERA-Interim, CFSR и NCEP-NCAR для оценки лавинной опасности в горах Северного Кавказа, которые предварительно сравнивали с материалами метеорологических станций (средние сезонные значения приземной температуры и осадков). Для расчёта лавинной опасности использовалась корреляционная матрица, основанная на связи показателя лавинной опасности со стандартными отклонениями сезонных значений температуры и осадков. Установлены синоптические процессы, способствующие формированию катастрофических лавин. Показано, что аномально высокая лавинная опасность возникает при отрицательной аномалии температуры воздуха у земли и на высотах при близком к норме интегральном влагосодержании атмосферы
Сравнение гидротермической структуры двух ледников Шпицбергена и Тянь-Шаня по данным радиозондирования
Get PDFThe distribution of cold and temperate ice and water in polythermal glaciers significantly affects their dynamics, thermal and hydrological regime. Radar techniques are an effective remote method of their studies that allows one to determine a glacier thickness by the delay time and to estimate the water content in temperate ice and at bedrock by the intensity of reflections from the interface between cold and temperate ice and the glacier bed. In case study of Austre Grønfjordbreen in Spitsbergen and Central Tuyksu glacier in Tien Shan we consider the features of their hydrothermal structure in spring and summer periods using the data of ground-based radio-echo sounding at frequency of 20 MHz. To estimate the relative water content, we used data from measurements of relative power reflections from the cold-temperate ice interface, at the bedrock, and from the temperate ice body. In these glaciers (Austre Grønfjordbreen and Central Tuyksu), the average thickness of cold and temperate ice is, respectively, 61 ± 6 and 27 ± 2 m, and 39 ± 4 and 20 ± 2 m, the volume of cold ice is 0.466 ± 0.005 km3 and 0.044 ± 0.002 km3, and volume of temperate ice is 0.104 ± 0.001 and 0.034 ± 0.001 km3. Warm ice contains 2080 × 103 and 680 × 103 m3 of water, respectively, with an average content of 2%. Measurements along the longitudinal profiles of these glaciers showed that in some parts on Austre Grønfjordbreen in the spring period the average intensity of reflections from the coldtemperate ice interface and the bedrock is −0.02 – −26.3 and −6.0 – −11.8 dB, respectively, and at the whole profile this is −13.36 dB. At Central Tuyuksu glacier the spring values are −14.5 – −32.4 and −29.6 dB, respectively. We attribute such differences of glaciers to the different water content in the temperate ice below and above these boundaries, to the specific distribution of the ice facies zones and glacial nourishment, to the different intensity of surface melting in the spring and summer periods, and to the different crevassing and velocity of glaciers.Рассмотрены особенности распределения толщины холодного и тёплого льда и воды в политермических ледниках на Шпицбергене (Земле Норденшельда) и Тянь-Шане (Заилийский Алатау) по данным наземных радиолокационных измерений на частоте 20 МГц, выполненных соответственно весной 2010 и 2019 гг. и летом 2013 г. По времени запаздывания и интенсивности отражений от поверхности раздела холодного и тёплого льда из толщи тёплого льда и от ложа определены толщина и объём холодного и тёплого льда, оценено содержание воды в тёплом льду и показана связь этих характеристик с особенностями строения и режима ледников в весенний и летний периоды, до и после начала таяния
Проявление климатических изменений в ледовом режиме Ладожского озера за последние 55 лет
Get PDFThe article presents results of monitoring changes in some phenological characteristics of the ice cover of Lake Ladoga over the past 55 years. A steady tendency has been observed for a decrease in the duration of ice formation and the area of fast ice since the beginning of the 90s. A comparison is made of the average spatial patterns of ice formation dynamics between the periods 1964–1994 and 1993–2019. Since the beginning of the 90s, there has been a change in the ice characteristics of Lake Ladoga, directly related to a reduction in the duration of the cold period. The duration of ice events averaged over the past 30 years has decreased by about a month compared with the previous thirty-year period. Fast ice began to cover only 30% of the lake surface compared to 80% in previous years. The frequency of winters with incomplete freeze-up (remaining ice free areas) increased from two to six years per decade. The warming effect is most clearly seen in the central part of the lake. Such significant changes in the dynamics of ice phenology cannot but affect the functioning of the entire ecosystem of Lake Ladoga.Представлены изменения некоторых фенологических характеристик ледяного покрова Ладожского озера за последние 55 лет. Установлена устойчивая тенденция уменьшения продолжительности ледообразования и площади припая с начала 1990-х годов, что связано с сокращением продолжительности холодного периода. Выполненное сравнение осреднённых пространственных закономерностей динамики ледообразования за периоды 1964–1994 и 1993–2019 гг. с перекрытием в один год позволило выявить уменьшение во второй период примерно на месяц по сравнению с первым 30-летним периодом средней продолжительности сплошного ледостава
Южный океан – суровая морская окрестность ледяного континента
Get PDFThe latest in a series of Great Geographical Discoveries was the finding of a southern ice continent in 1820. It was long expected, but very late for different reasons. Among the main ones are the physical and geographical characteristics of the Southern Polar Region of the Earth, which was discovered much earlier than the Northern one. Geographers and sailors, confident in the polar symmetry of the planet's surface, found it difficult to imagine the location of the still unknown continent so close to the South Pole. In addition, the vast belt of water and ice in the Southern Ocean surrounding Antarctica was (and still is) a serious obstacle to safe navigation. Other reasons were the results of James Cook's Second circumnavigation of the world in 17721775 to search for the Southern Mainland. In 1773, Captain D. Cook on the ship "Resolution" for the first time crossed the Southern Arctic Circle and reached 71° s. s. He considered the voyage in the Southern Ocean quite successful: the Southern hemisphere was sufficiently explored and the search for the Southern continent was put to an end. The authority of the English navigator was so high that nobody tried to refute his opinion for almost half a century. It required not only the courage of scientific foresight, but also the power of a state with a developed shipbuilding industry, skilled sailors and experience of long successful voyages in the World's oceans. At the beginning of the XIX century, Russia having the status of the Ocean Power possessed all this. According to the plan of the Russian Navy Department, the Russian Antarctic Expedition of 1819–1821 was aimed at implementation of scientific exploration in the least studied and most inaccessible high latitudes of the Southern Ocean. One of the participants in the preparation of the expedition, Captain Irank I.F.Krusenstern, wrote that this expedition "is for exploring the countries around the South Pole with greater accuracy than how much is known about them to this day...". In search of Antarctica, the naval sloops “Vostok” and “Mirny” had to cross the "roaring forties" and "furious fiſties" of the southern latitudes and overcome the belt of driſting icebergs and polar ices.Пояс бурных вод, льдов и айсбергов Южного океана – суровое препятствие навигации. Это повлияло на итоги второго кругосветного плавания Д. Кука в 1772–1775 гг. Кук считал плавание успешным: Южное полушарие достаточно исследовано и поискам Южного континента положен конец. Открытие шестого материка русскими было предопределено господствовавшими научными воззрениями на соотношение океана и суши на Земле и симметрию её полярных областей. Русские военные моряки на шлюпах «Восток» и «Мирный» под командованием Ф.Ф. Беллинсгаузена в беспримерном кругосветном плавании в Южном океане в 1819–1821 гг. открыли первые антарктические земли – остров ПетраI и Землю Александра I в широтах 68–69°, что уже тогда позволило наметить северные границы Антарктиды
Гляциоклиматические исследования Института географии РАН в кратере Восточной вершины Эльбруса в 2020 г.
Get PDFDuring the field campaign in August 18–30, 2020 the meteorological regime and heat balance of the glacier surface were investigated in the crater of Mt Elbrus Eastern Summit (5600 m a.s.l.) together with the GPR measurements of the ice thickness and seasonal snow cover. Preliminary data analysis allowed the following features: the predominance of synoptic fluctuations over the diurnal ones; the high values of average and maximum wind speed associated with the impact of jet streams and with influence of leeward storms; extremely high temporal variability of relative humidity and its very high deficit in cloudless conditions conducive to intensive evaporation and sublimation from the snow surface. The maximum thickness of ice in the crater reaches 100 m, and the average is 34 m. A new ice core with a length of 96.01 m from the glacier surface to its bed had been obtained. The drilling speed varied from 11 to 1 m/h, decreasing with depth from 4.5 to 4.0 m/h on average. The thickness of the snow-firn mass is about 20 m, which is three times less than on the Western Plateau of Mt Elbrus. According to measurements in the borehole, temperature at the glacier bed is −0.6 °C. The calculated heat flux is 0.39 W/m2. Air sampling was carried out in the crater of the Eastern Summit of Elbrus and on the Garabashi glacier. Repeated measurements of the soil temperature in the fumarole field on the outer edge of the crater of the Elbrus Eastern Summit allow the conclusion that the temperature regime is stable.С 18 по 30 августа 2020 г. в кратере Восточной вершины Эльбруса впервые проводились наблюдения за метеорологическим режимом и тепловым балансом ледника. Выполнена также радиолокационная съёмка толщины льда и сезонного снежного покрова, пробурена скважина от поверхности до ложа с получением керна льда, измерены температуры в скважине, в шурфе из сезонной снежной толщи отобраны образцы для изотопного, химического и спорово-пыльцевого анализа, на поверхности фумарольного поля и в атмосфере над ледником взяты образцы газа, продолжен мониторинг температуры грунта на фумарольной площадке
Возникновение термической конвекции в мохово-снежном покрове побережья залива Грёнфьорд (Западный Шпицберген)
Get PDFThe significant part of the Arctic soils is covered by vegetation all year round, to which a layer of snow is added in winter. Both layers have a similar structure, consisting of a skeleton (organic and ice, respectively) and air-saturated pores, and, thus, form a unified system with high heat-insulating properties. But, with the temperature gradient within the layers, convection can arise, which significantly reduces the thermal resistance of the layers and affects the heat, mass and gas exchange of the atmospheric boundary layer with the ground. In this connection, the role of convective transport in the formation of the thermodynamic and biogeochemical regime of polar ecosystems becomes obvious. Note that the role of convection in the snow cover is discussed in literature, but similar studies for vegetation are absent. This is one of the reasons why the processes of heat and mass transfer in the moss-snow layer above the ground in high latitudes are reproduced in a very simplified way, even in the most advanced models of the Earth system. In this paper, we study the occurrence of instability in a system of two porous layers with heat-insulated boundaries for conditions that approximate the snow and vegetation cover of the Arctic tundra on the coast of the Gulf of Grenfjord (West Spitsbergen). The analytical solution of the Rayleigh-Darcy problem is obtained by means of expansion of the amplitudes of perturbations of vertical velocity and air temperature into series. The dependence of the convective instability threshold on the variations of the thermal physical properties of the vegetation and snow cover of the studied region, parameterized according to measurement data and literature sources, is estimated. It has been found that the stability threshold increases with growth of snow thickness and density. It was also shown that the non-Rayleigh instability becomes impossible when heated from above (meaning the long-wave mode), which occurs in a similar system of two layers of homogeneous immiscible liquids due to the difference in their thermal physical properties.С использованием метода малого параметра получено аналитическое решение задачи Рэлея– Дарси для двухслойного мохово-снежного покрова арктической тундры побережья Западного Шпицбергена. Оценена зависимость порога длинноволновой конвективной неустойчивости от теплофизических свойств слоёв, показаны качественные отличия рассмотренной задачи от аналогичной задачи для однородных жидкостей
Оценка объёма айсбергового стока с выводных ледников Северной Земли за 2014–2019 гг.
Get PDFVolume of icebergs calved from the output glaciers located on the Northern Land during 2014–2019 was estimated using the satellite information. High-resolution satellite data were obtained in the visible spectral range from the non-commercial satellites Sentinel‑2 (spatial resolution 10 m) and Landsat‑8 (spatial resolution 15 m). Data collection was carried out under conditions when the natural illumination in the Arctic was sufficient (March–September) to make pictures in the visible spectral range. About 100 satellite images were analyzed for each year of the above period. The technique used for the iceberg detection is based on statistical criteria for finding the gradient zones in the analysis of two-dimensional fields of satellite images. The generation of the iceberg from a particular glacier was verified by using a form template of the detected iceberg taking into consideration the following parameters of the object: the geometrical shape, dimensions, specific features of «picture» of the ice surface (presence and orientation of cracks, peaks, and lakelets of melt water). The iceberg height was determined by its shadow on the image. The calculated total annual volume of icebergs from the outlet glaciers was estimated 1.52–1.9 km3. According to satellite data, the annual area reduction of the Northern Land outlet glaciers averaged 13 km2. The greatest contribution is made by 12 outlet glaciers located on the Komsomolets and the October Revolution islands. Of these, six are from the Academy of Sciences ice dome, four – the glaciers of the Matusevich Fjord, the Vavilov Glacier and the Rusanov dome glacier № 12. Icebergs of maximum height (30–40 m) are produced by glaciers of the North-Eastern slope of the Academy of Sciences ice dome and glacier № 12 of the Rusanov dome. In general, according to satellite data of recent years, generation of icebergs from the outlet glaciers of the Northern Land shows a steady growth trend.По спутниковым данным видимого спектрального диапазона оценена продуктивность выводных ледников Северной Земли как источников айсбергов в период 2014–2019 гг. Рассчитанный ежегодный суммарный айсберговый сток с выводных ледников составил 1,52–1,9 км3. Наибольший вклад в айсберговый сток вносят выводные ледники ледникового купола Академии наук и шельфовый ледник Матусевича. Согласно спутниковым данным последних лет, айсберговый сток выводных ледников Северной Земли имеет устойчивую тенденцию к росту
Оценка эффективности противолавинных мероприятий на горнолыжном курорте «Красная Поляна»
Get PDFFor the first time, a qualitative and quantitative evaluation of the effectiveness of anti-avalanche measures was carried out for the territory of the «Krasnaya Polyana» ski resort, located in the Western Caucasus on the Aibga ridge. The following materials were used for this work: the results of field survey in 2019, which made it possible to map the resort's infrastructure exposed to possible snow avalanches and protected by existing preventive (anti-avalanche) measures, experience of similar studies from other regions as well as identification of the avalanche release zones by means of digital elevation model and analysis of remote sensing data, archive data on the snow avalanches regime at the site, and numerical modeling of the snow avalanches with different starting conditions. Modeling of the avalanches was performed in the RAMMS program basing on three scenarios: 1) taking account of the successful operation of existing anti-avalanche measures; 2) with regard for the failures in the work of existing anti-avalanche measures that were recorded earlier during the operation of the resort; 3) without considering any anti-avalanche measures, which corresponded to the conditions at the stage of the territorial planning of the resort. Differences in the impact of simulated avalanches on the resort infrastructure were interpreted as «high», «medium» and «low» effectiveness of existing antiavalanche measures. It was found that the dynamical characteristics of the local avalanches (run-out distance, volume, velocity, and pressure) had different importance for different types of the infrastructure with regard to the effectiveness of anti-avalanche measures. Under existing conditions of the relief, climate and vegetation of the investigated territory the artificial triggering (at the ski resort it is mainly made by the Gazex systems) is the most efficient. Snow-retaining structures often do not perform their functions, while dams and avalanche cutters can be successful only in combination with the properly functioning artificial triggering. It was found that there are areas where the run-out distance of artificially controlled avalanches is smaller than that of possible natural avalanches, and these areas can still be dangerous for the infrastructure of the resort due to the high values of the avalanche speed and pressure.Впервые на основе предложенного в работе комплексного подхода выполнена оценка инженерно-географической эффективности всех видов противолавинных мероприятий, применяемых на горнолыжном курорте «Красная Поляна», с использованием метода математического моделирования лавин. В условиях рельефа, климата и растительности исследуемой территории искусственно регулируемый сброс лавин (в основном осуществляемый системами Gazex®) наиболее эффективен. Снегоудерживающие сооружения не всегда выполняют свои функции, в то время как дамбы и лавинорезы могут быть эффективными только в комплексе с искусственно регулируемыми сбросами лавин. Предложенная авторами методика оценки эффективности методов защиты от лавин может использоваться при планировании противолавинных мероприятий, позволяя снижать экономические затраты при организации и функционировании курортов