Ice and Snow (E-Journal) / Лёд и Снег
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Об обратной связи доли лавинного питания с аккумуляцией ледника
Get PDFReleases of avalanches are an important factor of snow accumulation for many mountain glaciers. However, the quantitative estimate of the share of avalanche snow in the incoming part of the mass balance has not yet been standardized due to the lack of a universal methodological scheme for the calculation and collection of actual material. In rare cases, e.g. for the Djankuat Glacier in the Caucasus, this problem is partly solved. Here, the conceptual basis of the required calculations is created, and the input information has been supplied for many years by the route snow-measuring profling performed in the spring close to the date of the maximum of seasonal snow reserves and accompanied by direct feld mapping. Annually, avalanche deposits attributed to additional snow income from outside the glacier are recorded in all high-altitude morphological zones, with the exception of the lowest (< 2850 m) hypsometric belt, although in the half-century history of monitoring there were cases when snow avalanches reached it. Te volume of avalanche deposits was calculated for 15 years afer 1991/92, and each time it correlated with the gross snow accumulation of the corresponding balance year. Te contribution of snow avalanches to the income of substances on the glacier varies from 1.8 to 10.0% and averages 4.7%. Paradoxical (but only at frst glance) conclusion based on the analysis of data on volumes of avalanche and total accumulation is the feedback of these indicators (r = -0.58). It should be noted that the share of avalanche contribution to alimentation of the glacier has a more convincing feedback with accumulation and background snow content of winter (r = -0.72). Probably, the revealed tendency of increasing role of the additional avalanche alimentation in low-snow years (and vice versa) is not limited by the only reference object, and it is true for any glacier prone to the avalanche influence.На основе полевых измерений и вычислений по оригинальной методике рассчитана доля лавинного питания ледника Джанкуат за 15 сезонов. Вклад снежных лавин в приход вещества варьирует от 1,8 до 10,0% и в среднем составляет 4,7%. Установлено, что доля лавинной подпитки и абсолютные объёмы лавинной аккумуляции связаны обратной зависимостью с фоновой снежностью зимы и общим объёмом накопившегося на леднике зимнего снега
РОСТ ПРИПАЯ И ЕГО ВЛИЯНИЕ НА ЗАМЕРЗАНИЕ ВЕРХНЕГО СЛОЯ ДОННЫХ ОТЛОЖЕНИЙ В ПРИБРЕЖНОЙ ЗОНЕ ГУБЫ БУОР-ХАЯ (МОРЕ ЛАПТЕВЫХ)
Get PDFResults of the ice and hydrological measurements carried out in the winter of 2014/15 in theTiksiGulf(Buor-KhayaBay) are described. These data served a basis for development of a conceptual thermodynamic model of seasonal freezing of the sea water layers and underlying bottom sediments in the sea-shore zone. The model uses two methods of localization of the phase transition zones: a classical (frontal) one is used for water, while another one within the range of temperatures – for the bottom. For real atmospheric conditions, we investigated specific features of the water freezing through in the shallow coastal zone of theLaptev Sea. The quantitative characteristics of the process were obtained. The calculations demonstrated that the distinguishing feature of the process is a stabilization of the ice thickness, taking place due to essential increasing of a salinity of the sea water. As a result of this, a shallow water body does not frozen through down to the bottom at even the very low air temperatures. Cooled salt waters does not allow liquid to be frozen in pores of the bottom ground. Salinization of the under-ice water layer can cause the melting of fast ice in the shallow water with its simultaneous increase away from the coast. Ice formation in water layers and bottom sediments begins at the same time, although it proceeds differently at different depths. Due to salinization of the bottom ground a continuous frozen zone is not formed, and the whole layer of freezing precipitation is a two-phase (partially frozen) area. As a whole, the model estimates of the process parameters including the motions of the phase fronts agree with known data of direct measurements. Despite such conformity, the model data should be considered as only evaluative ones. If a bottom is flat, the horizontal mixing and advection, which are not reproduced by a one-dimensional model in principle, the actual salinity parameters will most likely not reach the calculated values. However, for small values of the tides in theBuor-KhayaBayand insignificant reverse flows of salt, effect of the last ones does not apparently exert significant influence on the intensity of cooling of the under-ice water layer as well as on the ice formation in upper layers of the bottom within such time scales as a season.Представлены и проанализированы данные стандартных ледовых наблюдений зимой 2014/15 г. в бухте Тикси (губа Буор-Хая, южная часть моря Лаптевых). Описаны особенности изменчивости поля температур в припайном льду и подлёдном слое моря. Данные наблюдений дополнены модельными оценками замерзания слоя воды и верхних слоёв донных отложений
ОСОБЕННОСТИ ПРОСТРАНСТВЕННОЙ ДИФФЕРЕНЦИАЦИИ СНЕЖНОГО ПОКРОВА В НИЗКОГОРНЫХ ЛАНДШАФТАХ РУССКОГО АЛТАЯ (НА ПРИМЕРЕ БАССЕЙНА Р. МАЙМА)
Get PDFThe paper presents results of snow route measurements carried out during two winter seasons (2014/15 and 2015/16) over the period of maximum snow accumulation. The region of investigation was mainly the lowmountain basin of the river Maima (North, North-East Altai). Meteorological conditions for these periods (amounts of precipitation and mean monthly temperatures) were compared with climatic data (1985– 2016). The results obtained allowed establishing a relationship between the spatial and temporal variability of the snow depth, density and SWE (snow-water equivalent) and the weather conditions, orographic features (exposure and steepness of slopes), and characteristics of the underlying surface. The winter of 2014/15 was warm and moderately snowy season, while the winter of 2015/16 was warm but with small amount of snow. At the subtype level of the landscapes the maximum values of the snow cover thickness and the snow storage were observed in the chern-taiga landscapes, and the smallest ones – in the sub-taiga part of the basin area. The maximum snow storages (SWE) are characteristic for the secondary small-leaved forests and meadows, where these values exceed similar ones under the indigenous fir trees by 30%.The paper presents results of snow route measurements carried out during two winter seasons (2014/15 and 2015/16) over the period of maximum snow accumulation. The region of investigation was mainly the lowmountain basin of the river Maima (North, North-East Altai). Meteorological conditions for these periods (amounts of precipitation and mean monthly temperatures) were compared with climatic data (1985– 2016). The results obtained allowed establishing a relationship between the spatial and temporal variability of the snow depth, density and SWE (snow-water equivalent) and the weather conditions, orographic features (exposure and steepness of slopes), and characteristics of the underlying surface. The winter of 2014/15 was warm and moderately snowy season, while the winter of 2015/16 was warm but with small amount of snow. At the subtype level of the landscapes the maximum values of the snow cover thickness and the snow storage were observed in the chern-taiga landscapes, and the smallest ones – in the sub-taiga part of the basin area. The maximum snow storages (SWE) are characteristic for the secondary small-leaved forests and meadows, where these values exceed similar ones under the indigenous fir trees by 30%
ФОРМИРОВАНИЕ ГЕОХИМИЧЕСКИХ АНОМАЛИЙ ПРИ МИГРАЦИИ УГЛЕВОДОРОДОВ В КРИОЛИТОЗОНЕ ЗАПАДНОЙ СИБИРИ
Get PDFClimate warming can be caused by global changes due to emissions of the greenhouse gases, which are mainly carbon dioxide and methane. Although vertical migration of hydrocarbons (seepages) to the surface from oil and gas fields has been known for many years, this important environmental factor has not yet received due attention in the study of the Arctic and Subarctic regions. The major hydrocarbon-induced chemical and mineralogical changes within the permafrost stratum were investigated in the south of theTazPeninsulainWestern Siberia. The samples of frozen core from the deep (35 m) hole, which had been drilled from the top of hydrolaccolite, were examined to analyze the cryogenic texture of the frozen rock mass, to estimate the gas content in rock and ice, and to determine the authigenous mineral association using SEM and EDX spectroscopy analysis. It is shown that the migration of hydrocarbon gases through the permafrost stratum is caused by shear deformations with the formation of cryogenic crack-type textures on the sliding surfaces, which are characterized by the presence of gas-saturated ice crystallites and high jointing of quartz. It has been established that the migration of hydrocarbons, primarily methane, frozen in sedimentary strata causes significant changes of the pH/Eh parameters: local anaerobic conditions may be changed by microaerophilic ones through the formation of oxygen during crystallization of the water in the slide area; mainly neutral and weakly acidic conditions can locally be changed by the alkaline ones due to the cryogenic concentration of chlorides during freezing. It was found that the impulse character of hydrocarbon migration in permeation zones of frozen strata causes mosaic distribution of sulfate and iron reduction processes, which control the neogenesis (including as a result of microbiological processes) of various forms of iron compounds: sulfides – carbonates oxides.Рассматриваются геохимические процессы при миграции углеводородных газов по данным изучения мёрзлых отложений на территории юга Тазовского полуострова. Миграция газов обусловлена деформациями сдвига с образованием криогенных текстур с присутствием газонасыщенных кристаллитов льда по поверхностям скольжения. Импульсный характер миграции обусловливает микромозаичное распределение процессов сульфати железоредукции, которые ведут к образованию, в том числе и с участием микробиологических процессов, различных форм железа: сульфидов, карбонатов, оксидов
Современные изменения площади ледников западной части Земли Норденшельда (архипелаг Шпицберген)
Get PDFClimate warming in Svalbard, starting in the 1920s, caused a signifcant reduction in the mountain glaciation of the Nordenskjold Land. Te most extensive changes took place in the Western part of this territory due to the influence of the warm Spitsbergen current creating here the high temperature background. In addition, due to elevation of the level of the climatic snow line, many glaciers have actually lost the area of accumulation. From 1936 to 2017, the area of glaciers in the Western part of this region decreased by 169.5 km2 or 49.5%. Large valley glaciers and numerous small glaciers have lost the greatest area. Te relative losses of the area of glaciers were revealed to be proportional to sizes of them. In average over the past 80 years, glaciers with areas smaller 0.5 km² reduced by 76%, while big glaciers with areas larger 5 km2 – by only 34%. At present, there are 152 glaciers with a total area of 172.73±9.31 km2 in the Western territory of the Land of Nordenskjold (West of the Bolterdalen valley). According to the aerial photography of 2008–2009, the total area of glaciation of the Land of Nordenskjold covers 428 km2. High present-day rates of the retreating of local glaciers are apparently caused by extreme thinning of glacial tongues. At the same time, shrinking of glaciers located in the West of the Peninsula turned out to be more intensive than that of glaciers in its center. Although the Eastern territories receive less precipitation than glaciers near the coast of the Greenland Sea, the Eastern glaciers were found to be more resistant to reduction due to higher locations of them.Приведены данные об изменении площади оледенения западной части Земли Норденшельда с 1936 по 2017 г. Сокращение ледников в результате повышения летних температур воздуха зависело от их размеров, высотного положения и экспозиции и в целом составило 169,5 км², или 49,5%. Больше всего сократились площади ледников на побережье Гренландского моря
Всероссийская научная конференция «Тематические и междисциплинарные исследования в Арктике и Антарктике»
Get PDF.3–5 октября 2016 г. в Сочи была проведена Всероссийская научная конференция «Тематические и междисциплинарные исследования в Арктике и Антарктике». Это была 12-я по счёту конференция этой тематики, собравшая более 60 участников. Конференцию организовали Научный совет РАН по Арктике и Антарктике, Институт географии РАН, Арктический и Антарктический научно-исследовательский институт, Сочинский научный центр РАН при финансовой поддержке Федерального агентства научных организаций и гранта РФФИ № 16-05-20701. На конференции обсуждались основные направления полярной науки. В настоящем обзоре приведены результаты, наиболее тесно связанные с гляциологией и геокриологией
Снежный покров на Лагонакском нагорье (Западный Кавказ)
Get PDFThe paper presents characteristics of a snow cover observed on the Lagonaky high plateau (the Western Caucasus) in the interfluve of the rivers Belaya and Pshekha along two snow-measuring courses. The period of observations is 1973–2015, and the altitude interval is 460–2020 m. The characteristics measured are the following: depths of snow cover, the snow density, and temperature of different snow layers in the test pits. The stratigraphy of the snow thickness is described. In different years, observations did show changes in the depths which felt within a wide range of values from a few centimeters up to 5–6 m at the same points. The observations allowed determination of dates of snow appearance (setting-up of snow cover) as well as the disappearance in different parts of the Lagonaky high plateau. Durations of the snow cover in different altitudinal belts were also determined. By the end of March the snow cover disappears to altitudes of 700 m, and after 20th of April the slopes become free of snow to 1000 m. The snow cover duration in the low-altitude zone (500–1000 m) is 70–80 days, while in the middle altitudes (1,000–1,500 m) it is 130 days. In the highlands (above 2000 m), the snow cover lasts for 215 days. It must be emphasized that during the last five years the duration of snow cover has changed significantly. Materials of snow surveys showed that snow depths and water contents (water equivalents of snow cover) significantly differ from year to year. In seasons 1975/76, 1978/79, 19861/87, 1989/90 the winters were extremely snowy, while winters in 1976/77, 1979/80, 1983/84, 1990/91, 2013–2015 had small amount of snow. According to data of distant snow-measuring sticks, the maximum values of the snow depth (610 cm) have been recorded in March of 1976 near the tourist shelter Fisht (1596 м). Significant changes in the distribution of snow cover in recent years were probably related to the global climate changes.Представлены новые данные о толщине, плотности снега и снегозапасах, полученные при сне-гомерных работах в 1976–2015 гг. на Лагонакском нагорье в бассейне р. Белая. Проанализиро-вано распределение снежного покрова и продолжительность его залегания по высотным зонам.Отмечено уменьшение снежности зим за последние годы, видимо, обусловленное общим потеплениемклимата
Применение методов машинного обучения для моделирования толщины снежного покрова
Get PDFSnow exerts significant regulating effect on the land hydrological cycle since it controls intensity of heat and water exchange between the soil-vegetative cover and the atmosphere. Estimating of a spring flood runoff or a rain-flood on mountainous rivers requires understanding of the snow cover dynamics on a watershed. In our work, solving a problem of the snow cover depth modeling is based on both available databases of hydro-meteorological observations and easily accessible scientific software that allows complete reproduction of investigation results and further development of this theme by scientific community. In this research we used the daily observational data on the snow cover and surface meteorological parameters, obtained at three stations situated in different geographical regions: Col de Porte (France), Sodankyla (Finland), and Snoquamie Pass (USA).Statistical modeling of the snow cover depth is based on a complex of freely distributed the present-day machine learning models: Decision Trees, Adaptive Boosting, Gradient Boosting. It is demonstrated that use of combination of modern machine learning methods with available meteorological data provides the good accuracy of the snow cover modeling. The best results of snow cover depth modeling for every investigated site were obtained by the ensemble method of gradient boosting above decision trees – this model reproduces well both, the periods of snow cover accumulation and its melting. The purposeful character of learning process for models of the gradient boosting type, their ensemble character, and use of combined redundancy of a test sample in learning procedure makes this type of models a good and sustainable research tool. The results obtained can be used for estimating the snow cover characteristics for river basins where hydro-meteorological information is absent or insufficient.На основе открытых данных гидрометеорологических наблюдений на трёх водно-балансовых стационарах, расположенных в различных физико-географических условиях, исследована возможность применения современных методов машинного обучения для моделирования динамики снежного покрова. Эффективность использования ансамблевой модели градиентного бустинга над решающими деревьями выше, чем моделей одиночного решающего дерева или адаптивного бустинга для всех исследуемых объектов
Холодный эпизод около 8200 лет назад в Северной Европе: анализ эмпирических данных и возможных причин
Get PDFCold episode in Northern Europe happened about 8200 years ago was known for a relatively long time, mainly due to paleobotanical (palynological) data obtained from analysis of lake and peat sediments. Detailed analysis of ice cores from the Greenland holes GRIP, GISP2, and NGRIP with a time resolution of about 10 years made possible to refine the duration and characteristics of the time structure of this cold period. This cooling lasted for approximately 160 yr. Spore-pollen analysis of lake sediments in Northern Europe (Sweden, Finland, Denmark, Germany, the North and North-West of Russia) and deep-sea cores of the North Atlantic showed that the mean annual air temperature during the maximum stage of the cooling was reduced by 1–2 °C, and in some areas by more than 3 °C. The cold spread from the coast of the North Atlantic into the European continent and manifested itself mostly in Sweden, Finland, the Baltic States, and to a lesser extent in the North-West and West of the Russian Federation. In the central Russia and North of 70°N the cooling was weak or absent. The question about a nature of this cold event and other cold spells in Late Glaciation, known as the cold of the early, middle and late Dryas, is widely discussed in the scientific literature. Most of scientists accept a hypothesis proposed more than 20 years ago, that the reduction of air temperatures in regions immediately adjacent to the North Atlantic was caused by the large volume of melt water discharged into the ocean as a result of disintegration and melting of ice-sheets. Climate models that take into account these effects allow estimating a decrease in the air and sea surface temperature due to freshening (desalination) of the upper ocean layer, and this confirms that the greatest decrease in temperature should be observed in the regions directly adjacent to the ocean. The increase in global temperature over the last 30 years is estimated to be 0.8 ± 0.2 °C, which is already reflected in a noticeable increase in precipitation in high latitudes. In addition, the melting of mountain glaciers and sea ice in the Arctic basin promotes freshening of the upper ocean, and as a result of these processes one can expect a certain decrease in the air temperature in the high latitudes if the present-day climate warming will continue. On the basis of paleoclimatic data, it can be assumed that such a decrease in air temperature can be relatively small and occur only in areas directly adjacent to the North Atlantic.Уже более 20 лет в Северной Европе известен холодный эпизод около 8200 лет назад. Похолодание продолжалось около 160 лет, температуры воздуха снижались на 1–2 °С, а в отдельных районах – более чем на 3 °С. Предполагается, что снижение температур воздуха было связано с поступлением больших объёмов пресной воды в Северную Атлантику в результате распада и таяния ледников. Подобный механизм имеет прямое отношение к оценкам будущего климата при развитии современного глобального потепления. Поскольку таяние горных ледников и морских льдов в Полярном бассейне способствует опреснению верхнего слоя океана, при развитии потепления в районах, непосредственно прилегающих к Северной Атлантике, можно ожидать некоторого снижения температуры воздуха в высоких широтах