Ice and Snow (E-Journal) / Лёд и Снег
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Применение методики компьютерной томографии для неразрушающего анализа ледниковых кернов
Get PDFComputed tomography (CT) is a nondestructive high-resolution way to investigate the three-dimensional structure of samples (ice, rock, etc.). The results of CT analysis of glacial cores consisting of firn and ice extracted on the Western plateau of the Elbrus Mountain (5100–5150 m a.s.l.) in the summer of 2017 are presented in the article. The core taken from the depth of 20.31–21.87 m and consisting of three sections (average length is 52 cm each) was analyzed. In order to maintain the natural negative temperature of the glacial core, a special cryothermos has been created. It conserved the temperature at the level of −25 °C. Data on the structural features of the samples and the three-dimensional pattern of the ice-firn density were obtained. Correlations between the density and some chemical elements had been established. The CT data made it possible also to determine sizes of ice crystals. Comparison of cross sections of cores with firn and ice thin sections (30 in total) has shown that the crystal structure is best displayed in the ice inter-layers since it is impossible to determine reliably sizes of the firn grains at the given survey resolution. Also, the use of the CT method made it possible to determine inclination of the firn layers within the ice core, which is caused by the inheritance of the slope of the surface microrelief and internal inhomogeneities of the firn thickness. Calculations showed that the angle of inclination of the layers varies from 6 to 9°.Методика компьютерной томографии позволяет получить снимки послойных срезов ледникового керна с помощью рентгеновских лучей. В работе представлен анализ кернов с Западного плато Эльбруса с помощью компьютерного томографа РКТ-180. Для поддержания естественных условий керна был создан специальный криотермос, который препятствует таянию образца и изменению структуры фирна во время съёмки. Исследована внутренняя структура керна, установлены размеры кристаллов в разных слоях, найдены неоднородности и получена трёхмерная картина плотности льда
Зимы лавинного максимума на Большом Кавказе за период инструментальных наблюдений (1968–2016 гг.)
Get PDFThis investigation has been carried out to identify winters with the maximum frequency of avalanches in the Greater Caucasus. The analysis was performed for decades and for the entire period of instrumental observations (1968–2016). We chose severe snow winters which were followed by releases of particularly large and heavy avalanches (Lmax) and the maximum area of damage to the mountain territory during the study period. The following materials were used for this work: 1) 47‑year-old (1968–2016) series of data on snow avalanches from observations performed at the high-altitude station of the Faculty of Geography of the Lomonosov Moscow State University in the near-Elbrus area (Central Caucasus); 2) the results of winter and summer investigations of snow and avalanches in Arkhyz (the Western Caucasus); 3) materials of field works carried out in the Caucasus at different times; 4) the results of winter typing from data of 41 mid- and high-mountain meteorological stations in the Greater Caucasus; 5) literature sources; 6) survey data. The dependence of avalanche activity on the types of winters was established for key observational sites in the near-Elbrus area (Central Caucasus) and Arkhyz (Western Caucasus). This dependence formed the basis for determining the Lmax winters from factors of the avalanche formation, i.e. the air temperature and precipitation for the cold period from meteorological observations. Based on the method of winter typing, the winters of the maximal avalanche occurrence were estimated from data of 41 meteorological stations of the Greater Caucasus for 1936–2016. Results of the typing revealed similar avalanche extremes as it was found from direct observations of releases of snow avalanches: on the Southern macro-slope of the Western and Central Caucasus – 1986/87; on the Eastern Caucasus – 1971/72. Two seasons, claiming the role of the Lmax – 1967/68 and 1975/76, were revealed on the Northern macro-slope.Дана оценка зим экстремального лавинообразоваия на Большом Кавказе по десятилетиям и за весь период инструментальных наблюдений (1968–2016). Использованы данные о сходе снежных лавин и результаты типизации зим по материалам 41 метеорологической станции Большого Кавказа. Установлено, что на южном макросклоне Западного и Центрального Кавказа к таким зимам относится 1986/87 г., на Восточном Кавказе – 1971/72 г., а на северном макросклоне – зимы 1967/68 и 1975/76 гг
Исследование ледников Арктики во время холодной войны: продолжение истории
Get PDFDuring the cold war, a secret Camp Century military base was created inside the ice sheet in the north-west of Greenland. At this station, the first deep ice core was recovered. It was a beginning of a new era in paleoclimatology – a continuous record of climatic changes over the past 100 thousand years was obtained. At the end of 2018, sediments from the bottom of the Camp Century ice core were discovered at the Niels Bohr Institute in Copenhagen. Their analysis showed that the age of the glacial stratum in this part of Greenland is about 400 thousand years. The history of the Camp Century establishment and glacier ice-core drilling is shown.Рассказано о строительстве внутриледниковой станции Camp Century в северо-западной Гренландии во время холодной войны, первом в мире глубоком керновом бурении ледника и о современных исследованиях, связанных с этими работами
Реконструкция зимней температуры воздуха раннего и среднего голоцена по изотопному составу ледяных жил восточного побережья полуострова Дауркина, Чукотка
Get PDFThe object of research is the Holocene massive ice veins on the Eastern coast of the Daurkin Peninsula, the easternmost part of the Chukotka. Peat bogs with ice veins occur on the surface of marine terraces (near Uelen and Lorino settlements) and on flood plain of the Koolen’ Lake; the thickness of peat varies from 0.7 to 2.5 m. Radiocarbon dating of the peat enclosing the investigated ice veins near Uelen and Lorino indicated that the beginning of peat accumulation began at the end of Late Pleistocene – early Holocene, about 11 cal ka BP. On the flood plain of the Koolen’ Lake peat bogs began to accumulate in the middle Holocene, i.e. around 6 cal ka BP. At the initial stage of peat bogs formation the rate of peat accumulation was high and could reach 1 cm/10 years. Ice veins occur at a depth of 0.5–1 m, and their lower parts are located in the underlying peat sandy loams and loams. In the upper levels of the peat bogs, narrow present-day ice veins are found, which are sometimes embedded in the upper parts of Holocene veins. A clear sign of syngenetic growth of veins is the upward bending of the layers of the host peat at the lateral contacts with the veins. The main source of water for the formation of ice veins is snow, as evidenced by the ratio of stable isotopes of oxygen and hydrogen and the values of deuterium excesses in the ice. A slight admixture of saline water (probably from a seasonally thawed layer) was noted in the veins near the Lorino settlement. Reconstructions of winter air paleotemperatures, performed on the basis of data of isotope-oxygen composition of ice from the veins, did show that at the period between 11 and 6 cal Ka BP, the mean winter air temperature on the Daurkin Peninsula was by 2–5 oC lower than today, but the air temperature of the coldest month (January or February) was still lower (by 4-8 oC) than today. The noticeable trend of increase of stable isotope values in the ice veins from early Holocene to the present time is indicative of a steady positive trend of mean winter air temperatures in the Holocene.Реконструкции зимних палеотемператур воздуха на основе данных изотопно-кислородного состава льда жил показали, что между 11 и 6 тыс. кал. лет назад среднезимняя температура воздуха была на 2–5оС ниже современной, а температура воздуха самого холодного месяца (января или февраля) – на 4–8оС ниже современной. Установлен устойчивый положительный тренд зимних температур воздуха от раннего голоцена до настоящего времени
Комплексное исследование старых торосов в Северном Ледовитом океане
Get PDFIn May 2015, the old hummock located to the North of the Bennett island (the East Siberian Sea) was investigated using several methods, among which were water thermal drilling, tachometric and sonar surveys, underwater video recording, as well as techniques to determine the strength and physical properties of ice. It was found out that only a combination of different methods provides a way to correctly estimate the main morphometric characteristics of a large ice formation and to determine its volume and mass. Analysis of the internal structure of the hummock, obtained by the water thermal drilling with a record of the drilling rate on the logger, made it possible to reveal a composite character of the ice formation (the hummock consisted of two fragments – the large old one and the smaller first-year piece) and to estimate approximately its age (3–4 years). Comparison of the main morphometric characteristics of the old hummock with the average values of first-year hummocks, investigated in the same area and the time, showed that the old hummock had significantly greater geometric parameters: its volume and mass exceeded similar parameters of the average younger formation by factors 5.6 and 5.8, respectively. This significant difference allows suggestion that the reason is not the age but a composite structure of the old formation. The average thickness of the consolidated layer of the old hummock equal to 4.6 m is almost twice larger than similar parameter of a first-year hummock (2.33 m) while the average value of the thickness in the old part of the old hummock (5.22 m) is larger than that of a young one by the factor 2.2. Note also, that the old hummock is characterized by almost complete smoothness (impossible to separate individual blocks) and minimal porosity (1%) of its ice. The salinity and density of the ice composing the frontal part of the old hummock is much smaller than in first-year hummocks. The average density of ice in the old hummock, determined analytically from the buoyancy condition, was equal to 896 kg/m3, while the average density of ice in the first-year hummocks, determined from measurements, – 917 kg/m3.На основе исследования морфометрии, внутренней структуры и физико-механических свойств старого тороса на северо-западе Восточно-Сибирского моря сделан вывод, что он состоит из более крупного старого и меньшего однолетнего фрагментов. Средняя толщина консолидированного слоя в старой части тороса больше, чем в среднем у однолетних торосов, в 2,2 раза
Изотопный состав атмосферных осадков и природных вод в районе Баренцбурга (Шпицберген)
Get PDFIn 2016–2017, during Russian Arctic Expedition on Svalbard (RAE‑S) we have collected the samples of atmospheric precipitation, terrestrial waters, snow and ice on Spitsbergen island in the vicinity of Grønfjorden. The measurements of stable water isotope content (δ18O and δD) in the atmospheric precipitation has allowed to draw the Local Meteoric Water Line (δD = 6,93δ18O − 0,35) and to analyze the relationship between the isotopic content and condensation temperature. Aside from this, the d-excess values in precipitation (dexc= δD − 8δ18O) was interpreted as a marker of the moisture source. It has been demonstrated that the isotopic content of the surface waters (lakes and rivers) clearly points to the dominating type of feeding (atmospheric, ground) of these hydrological objects. We have discovered the interannual variability of the isotopic composition of Lake Kongress water during 2 years and defined the sources of water in its tributes: 13 of them have atmospheric source and 9 – ground source. In general, isotopic content of water in the vicinity of Grønfjorden (mean values are: δ18O = −10,3 ‰, δD = −72,5 ‰) is higher than in other regions of Svalbard.Ключевые слова: атмосферные осадки, изотопный состав, природные воды, Шпицберген. Приведена интерпретация изотопных исследований проб воды, снега и льда, отобранных на ледниках Альдегонда, Западный и Восточный Грёнфьорд и в их долинах (озёра, снежники, реки), а также в долине оз. Конгресс. На основании анализа изотопного состава атмосферных осадков в посёлке Баренцбург в 2016–2017 гг. обсуждается использование изотопного состава как индикатора источника влаги для атмосферных осадков
Распределение и морфология современных ледников Камчатки
Get PDFThe current glacierization of the Kamchatka Peninsula includes 643 glaciers with a total area 769.48±48.34 km2. A variety of combinations of macro-relief factors, climate and volcanism caused irregular distribution of glaciers on the Peninsula, as well as the great variability of its characteristics in different areas. In quantitative terms, the prevailing glaciers here are the corrie (31.3%) and corrie-valley (12.8%) ones, but the largest areas are occupied by the transection-valley (26.6% or 204.42±7.56 km2) and the corrie-valley (16.5% or 126.78±9.77 km2) glaciers. The average area of the Kamchatka's glaciers is 1.2 km2, and it varies from 0.7 km2 in non-volcanic regions to 2.87 km2 in zones of active volcanism. The part of the largest (> 5 km2) glaciers in the total number of them and the total area is maximal (10.9 and 67.1%, respectively) in regions of active volcanism, and it is minimal (2.2 and 21.6%) in non-volcanic territories. As for the small glaciers (0.1–0.5 km2), the proportion of them in the total number and area is maximal (55.1 and 18.7%, respectively) in non-volcanic regions, and minimal (20.7 and 1.5%) in regions of active volcanism. The Kamchatka glacierization is characterized by various morphological types of glaciers. The transaction-valley glaciers cover the largest areas in regions of both the active volcanism (33.7% or 89.03±2.26 km2) and in non-volcanic ones (31.8% or 41.45±2.04 km2). In the regions of Quaternary volcanism, the dominating in areas are the corrie-valley glaciers (24.3% or 91.09±7.04 km2). The regions of active volcanism are characterized by the greatest variety of morphological types of glaciers. The largest part of the glaciation area of Kamchatka falls on the glaciers of the Western (24.7%), South-Western (22.3%) and Eastern (20%) exposures. But the glaciers of the Western (23%), North-Western (20.7%) and Eastern (15.1%) exposures are also predominant by quantity. The greatest vertical extent and average heights are characteristic of glaciers in areas of active volcanism, while the smallest ones occur in non-volcanic areas.С использованием современных спутниковых снимков и цифровых моделей рельефа определены морфологические типы и экспозиция ледников Камчатки по состоянию на 2002–2015 гг. Выявлены преобладающие по числу и площади морфологические типы ледников, распределение оледенения по склонам разных экспозиций, изменение размеров ледников и их высотного положения
Особенности летнего метеорологического режима Западного плато Эльбруса
Get PDFThe results of meteorological observations, carried out in the framework of the international project Ice Memory on the Western plateau of the Elbrus Mountain during the Second drilling expedition (24.06–17.07.2018), are analyzed. The analysis of the field data made together with the assessment of the large-scale meteorological fields from the NCEP/NCAR reanalysis did show that, on the whole, the observed meteorological conditions corresponded to the background state of the atmosphere in the Greater Caucasus in the summer season (with the exception of the anomalous high moisture content). The Western plateau is characterized by a high frequency of storm winds ( > 20 m/s) with low drifting snow and intensive snowfalls: the precipitation sum for the expedition period is approximately estimated as 150 mm. Spectral analysis of time series allowed establishing the significant role of the mountain and valley circulation in the formation of the meteorological regime. It is shown that the melting of snow in high-mountain conditions is determined by the incoming short-wave radiation, while turbulent flows of heat and moisture mainly transport energy from the surface. For 20 days of the observations, approximately 49 mm of snow (in the water equivalent) melted, and about 25% of this volume evaporated. The rest of the moisture diffused into the snow cover, and thus, remained in the accumulation layer. During the expedition, deviations of meteorological values from the norm were relatively small, so it can be assumed that the obtained value of the evaporated liquid on the Western plateau during the ablation period was close to the climatic mean.На основе результатов метеорологических измерений на Западном плато Эльбруса и с использованием глобального реанализа NCEP/NCAR дана количественная оценка типичных и экстремальных значений метеорологических величин, включая данные об осадках и таянии. Оценены компоненты радиационного баланса, турбулентный теплообмен, затраты тепла на испарение, диффузия тепла в толщу снега, и на этой основе рассчитаны возможные потери снега в области аккумуляции
Необычная книга
Get PDFPeter G. Knight. Glacier: Nature and Culture. London: Reaktion Books, 2019. 223 pPeter G. Knight. Glacier: Nature and Culture. London: Reaktion Books, 2019. 223
Динамика сезонно-талого слоя на Шпицбергене и Антарктическом полуострове в ХХI в. по результатам моделирования
Get PDFResults of modeling of the dynamics of the seasonally thawing layer in the twenty first century made for two polar points (the Svalbard Archipelago and the Antarctic Peninsula) are discussed in the paper. The loss of thermal stability of a permafrost is usually associated with the formation of non-merging layer that transforms then into a talik. This occurs when the seasonal thaw layer is not fully frozen due to a rise in air temperature and an increase in the snow cover thickness. Climate change (warming) causes an increase in the thickness of the seasonal thaw layer. From 2001 to 2018, the rise of summer air temperature at the Barentsburg weather station was about 0.05 °C/year, while in winter −0.21 °C/year, and at the Bellingshausen weather station (Antarctic) in the summer period a slight cooling was observed. On the island of West Svalbard in 1968–2000, the average daily summer and winter air temperatures were equal to +3.74 and −9.9 °C, respectively, while in 2001–2018 these values were significantly higher, especially in winter: +4.83 and −7.12°C, respectively. On the Antarctic Peninsula, similar values were equal to: +1.03 and −4.05 °C (1968–2000) and +0.83 and −3.60 °C (2001–2018). Calculations for the conditions of the Bellingshausen weather station did show that if the snow cover thickness exceeded 0.72 m (the average climatic value) but the average values of other parameters were not changed, formation of the non-merging permafrost became possible. With regard for a possible dynamics of the air temperature, the non-merging permafrost may be frozen through at the snow cover thickness lower 0.9 m. According to calculations for the conditions of the West Svalbard Island, it follows that when the snow cover thickness exceeds 1.5 m on the ground with its humidity higher 25% and the absence of moss cover, incomplete freezing of the seasonal thaw layer and the formation of non-merging permafrost becomes possible even at present time. Using data on rates of the air temperature rise and the regional model of the climate change, we show that at the soil moisture of 18% (it corresponds to measured values of air humidity) and the snow cover thickness of 1.5 m formation of a layer of non-merging permafrost may take place in 12 years, while at the thickness of 1 m – in 24 years.С учётом изменчивости летних и зимних температур воздуха и толщины снежного покрова на метеостанциях Баренцбург (архипелаг Шпицберген) и Беллинсгаузен (Антарктический полуостров) в начале XXI в. выполнены численные эксперименты по оценке динамики сезонно-талого слоя и времени формирования слоя несливающейся мерзлоты при разной толщине снежного покрова и влажности грунта