Ice and Snow (E-Journal) / Лёд и Снег
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Конвекция воздуха в снежном покрове морского льда
Get PDFFor the first time, data on stability of stationary convective filtration within infinite horizontal layer of snow covering the flat surface of floating ice is presented in this article. An analytical solution of the linearized problem was obtained with the use of the Galerkin method, and the parametric analysis of the problem was performed. It was found that the stability criteria (Rayleigh filtration numbers) obtained with consideration for the heat exchange of snow cover with the atmosphere did not exceed the known value of 4π2 for a horizontal porous layer with impermeable isothermal boundaries. As expected, the interaction with the atmosphere has the most significant impact on the critical Rayleigh numbers, while influence of variations in snow density and ice thickness and the thickness of the underlying layer of ice are small. Based on data of ice and meteorological observations made in the winter of 2015/16 in the Western part of the Laptev Sea together with calculations of the fast ice evolution, the values and temporal variability of temperature gradients and the Rayleigh numbers in the snow cover were obtained using a thermodynamic model. It was found that both, the model and observed magnitudes, exceeded their critical values determined by solving the stability problem. The conclusion is made that the convective regime of the heat transfer does really exist in the snow cover, and thus its contribution to the thermal and mass balance of sea ice during winter period should be taken into account.Построено решение задачи устойчивости воздуха в снежном покрове на морском льду. Рассмотрены различные варианты динамических и тепловых граничных условий, проведено параметрическое исследование задачи. Выполнено сравнение данных моделирования с результатами расчётов для реальных ледовых и метеорологических условий
Изотопная индикация источника воды для образования ледоминерального ядра торфяных миграционных бугров пучения
Get PDFIsotopic characteristics of ice cores of peat mounds (palsa) are considered. The distribution of the values of δ18O, δ2H, dexc and ratios δ18O–δ2H within the palza ice lense is associated with freezing in a closed or open system, and this allows finding the source of water for the ice formation. The use of computational modeling of the distribution of the values of δ18О and δ2Н during the ice formation in a closed system and the selection of the calculated parameters, performed in such a way that the actual values in the ice are described, show the initial isotopic characteristics of the moisture from which the ice was formed. The subject of investigation is the isotopic composition of segregated ice in the upper part of the ice core of a palsa near the Yeletsky settlement. Ice samples were obtained by drilling with a hand-held electric drill. In its upper part, the core is composed of frozen peat and loam. The source of water for the formation of segregated ice from this palsa was the atmospheric moisture with isotopic characteristics equal, on average, to: δ2Н = −106.7, δ18О = −15.3 and dexc = 15.7 ‰. These values correspond to the current atmospheric precipitation in the vicinity of the Amderma settlement. The water of the nearest bog did not serve as a source of water for the ice formation. The same conclusion, fully confirmed by the application of the calculated approach, was obtained for the hummocky massif of the Yukon (Canada). The calculation did show that the water from which the ice of the Canadian palsa was formed was a mixture of local atmospheric precipitation (80%) and the boggy waters of the peat plateau (20%). The presence of the last water is a possible indication to re-formation of mounds, when evaporated water from bog could participate in ice core formation.Рассмотрены изотопные характеристики ледоминерального ядра торфяных миграционных бугров пучения. На основе распределения значений δ18О, δ2Н, dexc и соотношений δ18O–δ2Н, а также выполненного моделирования льдообразования в закрытой системе сделаны выводы о происхождении воды, которая стала источником для льда бугров пучения типа пальза
Колебания ледников Северного и Южного ледниковых полей Патагонии по данным мониторинга с Международной космической станции
Get PDFQuantitative indicators of changes in 37 glaciers of the Patagonian Northern and Southern glacial fields were determined by means of decoding and analysis of photographs obtained by astronauts from the Russian segment of the International Space Station. On the basis of this information it was concluded that in 2002–2016 the glaciers of both fields of Patagonia continued to retreat. The frontal parts of the nine glaciers retained their positions, while others reduced at an average rate of several dozen up to 430 m/year. Repeated monitoring of 16 glaciers from this selection and analysis of the data obtained in 2016–2019 confirm this conclusion. The only exception was the O’Higgins Glacier, which did not change position of its frontal part for 12 years and then retreated in 2018–2019 to 1,250 m. In some cases, a gradual decrease in area of the frontal part of the glacier was accompanied by a sharp collapse of the lower zone with the formation of extensive fields of icebergs. The dynamics of the Bruggen Glacier (Pius XI) are not typical for the region under consideration: for many years this glacier has been advancing. This development cannot be explained without detailed field investigation in the area of snow and ice accumulation of the glacier. Perhaps that was due to a snow-drift transport in an extensive area of accumulation that supported the preservation of the size of the glacier tongue, and even its advance. According to our observations, the average rate of retreat of the glaciers of the Western and Eastern slopes of the Southern Ice Field significantly decreased since 2010, i.e. their degradation slowed down. At the same time, glaciers of the Northern Ice Field continued to decrease intensively.В результате анализа фотоснимков с Международной космической станции определены изменения 37 ледников Северного и Южного ледниковых полей Патагонии. В 2002–2016 гг. ледники обоих полей продолжали отступать, но их отступание с 2010 г. замедлилось, хотя некоторые ледники Северного ледникового поля продолжают интенсивно сокращаться. Лишь ледник Брюгген (Пия XI) на Южном ледниковом поле в течение многих лет наступает
Геофизические исследования внутреннего строения гляциально-мерзлотных каменных образований Центрального Алтая
Get PDFSeveral complexes of glacial-permafrost stone formations have been studied in the Central Altai using geophysical methods. The features of their internal structure together with characteristic differences between them depending on the dynamic activity, altitude and geomorphological characteristics were determined. Integration of the methods of the electrical resistivity tomography and the GPR-sounding made it possible to distinguish roofs on all the studied formations and to estimate thicknesses of the stone-ice cores. Studying of eight formations with different degrees of activity and located at different altitudes did show that the thicknesses of the stone-ice cores increase with height: from 8–10 m in the mid-mountain zone up to 18-20 m in the highlands. The values of the specific resistance of cores inside the glacial-stone formations are directly proportional to altitudes of the objects (the correlation coefficient is 0.7) that give an indication of increasing in the amount of ice in them with height. The depth of occurrence of the roof of the stone-ice material in the formations is more dependent on the exposure of the slope on which the object is located, and changes from 1–2 m on slopes of the Northern exposure up to 4–6 m on slopes of the Southern and Western exposures.C помощью комплекса методов электротомографии и георадиолокационного зондирования установлена глубина залегания и оценена мощность каменно‑ледяных ядер, а также прослежена взаимосвязь морфологии поверхности и внутреннего строения гляциально‑мерзлотных каменных образований Центрального Алтая
Ледовитость арктических морей и её связь с приземной температурой воздуха в Северном полушарии
Get PDFThe linear relationship between average monthly anomalies of the ice coverage in the Arctic seas and the surface air temperature over the land in the Northern hemisphere in March and September was analyzed for the purpose of finding regions with statistically significant correlations. Possible mechanisms of the revealed interrelations are discussed. Data on the surface temperature and the ice concentration from Met Office Hadley Centre were used in this study. A negative correlation of the sea ice with the temperature in the land regions adjacent to the seas, as well as a number of remote relations was revealed. Specifically, statistically significant relations were found between anomalies of the ice area in the Laptev Sea in September with the temperature anomalies in the Mediterranean region, as well as with the temperature anomalies in Central Asia. In most cases, such relationships may be explained by the influence of atmospheric circulation, including the North Atlantic Oscillation, the Arctic Oscillation, the Pacific Decadal Oscillation, and variability in the intensity of the atmospheric centers of action. Characteristics of seasonal variations of the sea ice coverage and climatic trends together with variability and autocorrelation of the coverage anomalies are considered. The largest reduction in the ice area is observed for the recent decades in the Barents Sea in winter while in the Kara, Laptev and East Siberian seas - in summer.Проанализирована линейная связь среднемесячных аномалий площади морского льда в арктических морях и приземной температуры воздуха над сушей Северного полушария в марте и сентябре. Установлена отрицательная корреляция с температурой в прилегающих к морям регионах суши, а также ряд удалённых связей, которые можно объяснить влиянием атмосферной циркуляции. Наибольшее сокращение площади морских льдов зимой в последние десятилетия наблюдаются в Баренцевом море, в летний – в Карском, Лаптевых и Восточно‑Сибирском морях
Лёд 0 в природной среде. Экспериментальные данные и предполагаемые области его существования
Get PDFThe paper presents the available experimental data on ice 0 and the assumed objects of the cryosphere in which it can exist. This ice is formed from supercooled volumetric water, and it precedes the formation of ices Ih or Ic, at temperatures below −23 °C. This crystalline modification has been recently predicted by computer simulations using methods of molecular dynamics. Ice 0 was then experimentally found by electromagnetic investigation of wetted nanoporous media. Interest in this modification of ice was aroused due to its special physical and chemical characteristics. A singularity of ice 0 is that it is a ferroelectric that has a high static dielectric constant. When ferroelectric ice 0 contacts other dielectrics at their boundaries a thin layer is formed due to the diffusion of electric charges, and its electrical conductivity is higher than that of the contacting media. High electrical conductivity in thin films allows investigating frozen dispersed media containing ice 0 using non-contact electromagnetic measurement methods. As this takes place, it becomes possible to register water freezing processes in objects existing at temperatures of −23 ÷ −100 C using microwave spectroscopy and remote sensing methods. It is assumed that ice 0 is involved in chemical transformations in different objects of the cryosphere – in the atmosphere, and vegetation and soil covers. Its formation in the pores of materials of man-made structures may exert influence on the life-time of mechanisms and structures at low temperatures due to increased electrocorrosion. Ice 0 is assumed to exist on cold planets and their moons. That is why studying the possibility of ice 0 appearing in different objects of the natural environment at negative temperatures is so important for understanding their properties and developing remote sensing methods.Приводятся сведения о недавно открытом льде 0. Эта кристаллическая модификация образуется из переохлаждённой воды при температурах ниже −23 °С. Лёд 0, представляя собой сегнетоэлектрик, характеризуется особыми физико-химическими свойствами. Его существование возможно в поровом пространстве искусственных сооружений и природных сред на Земле, холодных планетах и их спутниках
Вклад аномалий ледяного покрова Баренцева и Карского морей в изменение режима циркуляции и температуры Северной Евразии с середины 1990-х годов
Get PDFThe intra-seasonal features of changes in the surface air temperature in winter of the North of Eurasia are considered for the purpose to find a relationship between them and the reduction of the ice cover area in the Barents and Kara seas and the atmospheric circulation modes in 1979–2013. Regression estimates and analysis of the regional distribution of the relationship between winter temperature, geopotential height anomalies of 500 hPa and an index of the Scandinavian mode (Scand) with the ice cover area anomalies show that its autumn reduction contributes significantly to the formation of Arctic invasions and abnormal cold weather conditions in Northern Eurasia at the beginning of winter – in December and January. In February, which, according to the received estimates, is associated by 90% with the trend towards decreasing of the average winter temperature in the North of Eurasia since the mid-1990s, the linear dependence of the Scand index and the temperature anomalies on the autumn reduction of ice cover is not found. The stable dependence of cold anomalies in the North of Eurasia at the beginning of winter on the strengthening of Scand allows us to consider it the main circulation mechanism that determines the intensity, scale and regional structure of these anomalies. In turn, the connection of the Scand anomalies with the ice cover area of the Barents and Kara seas in October indicates their potential predictability, which can be used to predict the circulation conditions for the formation of abnormal frosts in Siberia and the European part of Russia in December and January.Оценки связи площади ледяного покрова в Баренцевом и Карском морях с показателями крупномасштабной атмосферной циркуляции и изменениями приземной температуры воздуха на севере Евразии в 1979–2013 гг. показывают, что линейная зависимость аномалий высоты геопотенциала 500 гПа и индекса Скандинавской моды (Scand) от осеннего сокращения площади ледяного покрова объясняет формирование арктических вторжений и распределение аномальных холодных температурных условий на севере Евразии в начале зимы (декабрь), но становится статистически не значимой в феврале
Воздействие ледяных образований на берега и дно мелководных морей и крупных озёр умеренных и субарктических широт
Get PDFIce formations affect linear and coastal structures not only in the Arctic, but also in the subarctic and middle latitudes. Most of the seas, lakes and bays, such as the Gulf of St. Lawrence, the Baltic, Black, Caspian Seas, and Sea of Japan, freeze partially or completely every year. Inland and northern lakes and seas of the Subarctic, such as the White Sea, the Gulf of Bothnia and the Sea of Okhotsk are characterized by the most severe ice conditions. Remote sensing methods are used to detect ice ridges and grounded hummocks. A side-scan sonar survey and echo sounding, along with the diving surveys, are used to detect the ice scours/furrows on the bottom. To study the ice-exaration relief on the exposed bottoms, remote sensing data and materials obtained by means of unmanned aerial vehicles (UAV) are used, along with field surveys. The pressure impact of ice on the land results in the formation of ice piles on shores up to 3–5 m high. This causes an intensification of the processes of destruction of the coast and the restructuring of the processes of relief formation. The ice pressure ridges up to 2–3 m high are widely distributed along the coasts. At the bottoms, typical ice scours (plowing furrows) have a dip along the central axis, as well as side and pressure rollers at the ends of the furrows. At the edge of the fast ice, multiple scours/furrows form a so-called «comb», usually oriented along the normal to the shoreline. The length of the largest furrows exceeds several kilometers; the width of individual ones reaches the first tens of meters, the systems of furrows - hundreds of meters; the depth of them can be down to 2 m. The maximal depth of the sea or lake at which impacts are possible can reach 30 m. Relic forms of ice and iceberg impact have also been studied in the middle latitudes. Traces of impacts of ice formations in the temperate zone have a low degree of preservation and are often concealed by sediments. The distribution of traces of ice impacts down to a depth of 30 m as well as to several hundred meters inland shows the scale of the process in temperate and subarctic climates. Ice heaps and thrusts are more common in mid-latitudes than in the Arctic.Рассмотрена рельефообразующая деятельность льдов на берегах и дне акваторий. Обсуждены региональные различия ледовых условий, параметры ледово-экзарационных форм и их сохранности, масштабы проявления процесса. Установлены основные различия ледовых воздействий в высоких и средних широтах
Реконструкция температуры деятельного слоя ледника на Западном плато Эльбруса за 1930–2008 гг.
Get PDFThe reconstruction of changes in the temperature of the base of the active layer (at a depth of 10 m) of the glacier on the Western plateau of Elbrus for the period 1930–2008 was performed. The temperature dynamics at this depth generally corresponds to the average annual changes in the air temperature at the height of the plateau (5100 m), since seasonal temperature fluctuations take place in the active layer. The initial data for the mathematical model are: 1) the temperature measurements in a borehole with a depth of 181.8 m, drilled on the plateau (2009); 2) vertical profile of the density of the firn/ice thickness; 3) vertical profile of the advection rate (ice speed), recently obtained from the analysis of the ice core (2015). Temperature changes are reconstructed by solving an incorrect inverse problem for the 1D heat equation with coefficients depending on the depth. The following conditions are added to the heat conduction equation: 1) the initial one that is calculated stationary temperature profile related to the beginning of the reconstruction period; 2) the boundary condition at the glacier bed – calculated permanent geothermal heat flux; 3) the condition of redefinition, i.e. distribution of the temperature measured in the borehole at the end of the reconstruction period. Solving the inverse problem, we obtain a previously unknown boundary condition on the surface which is the temperature of the active layer base as a function of time. The depth is reckoned from the base of the active layer. The method used for solving the inverse problem is the Tikhonov regularization, implemented numerically as an iterative procedure. The boundary condition on the surface (the restored function of the temperature changes) was found as a finite sum of harmonics with indeterminate coefficients. To improve the accuracy of the reconstruction, we used harmonic frequencies obtained from another indirect climate indicator – the tree-ring chronology for the Central Caucasus. Wavelet analysis was used to extract characteristic frequencies from the dendrochronological data. Our reconstruction determined the temperature changes within range from –17.7 to –15.3 °C for the investigated period. The reconstruction data were compared with independent polynomial smoothed temperature series from the studied region: with ENCEP/ENCAR reanalysis (significant correlation coefficient 0.76), as well as with temperature measurements at the Terskol (0.53) and Teberda weather stations. The reconstruction clearly reflects the main climate trends of the twentieth century: a warmer period in the 1940s, a colder period in the 1960s and 1980s, and extreme warming around 2000.На основе результатов измерения температуры в скважине глубиной 181,8 м, пробуренной в толще льда, материалов анализа ледникового керна и древесно-кольцевой хронологии выяснено, что температура основания деятельного слоя ледника (примерно 10 м ниже поверхности, где затухают межсезонные колебания температуры) за исследуемый период менялась в диапазоне от –17,7 до –15,3 °С, и это полностью соответствует изменению температуры воздуха в средней тропосфере в районе Эльбруса, оценённой по данным реанализа
Прорыв озера Прогресс (Восточная Антарктида): подходы к оценке характеристик прорывного паводка
Get PDFOn January 14, 2019, a breakthrough of water masses occurred on the Lake Progress (the oasis of the Larsemann hills, East Antarctica) with the formation of a flash flood. During the summer field seasons of the 63rd and 64th Russian Antarctic Expeditions (2017–2019), comprehensive hydrological, GPR and geodetic surveys were conducted in this area to ensure the safety of transport operations. The results of field measurements and calculations based on mathematical modeling of the breakthrough flood from the Lake are presented. The purpose of this study was to compare field observations and model calculations of the breakthrough flood and then to verify the existing model of Yu.B. Vinogradov on real data, since detailed observations of breakthrough floods of lakes of the Antarctic oases have not been previously carried out. The results of complex hydrological and geophysical investigations of LH73–Progress–Sibtorp lake system focused on areas where lake outburst are possible (snow-ice dams) made possible to formulate phenomenological model of the outburst process. It was emphasized that the lake water was discharged through a tunnel developed in the snow–ice dam, which subsequently evolved into a real riverbed. The maximum water discharge was formed approximately in 7.5 h after the start of the outflow, and it was estimated 5.4 m3s-1 according to the in-situ measurements, and 4.94 m3s-1 – by the model. The calculated volume of the flood is 76 320 m3. The differences between the model and in-situ measurements are about 9% that can be explained by the fact that the time of water retention by the snow-ice dam is not considered in the model.При исследованиях в 2018/19 г. в районе станции Прогресс (Восточная Антарктида) авторы наблюдали прорыв системы озёр Прогресс–Сибторп. Приводятся феноменологическое описание этого процесса, а также результаты наблюдений и математического моделирования