Ice and Snow (E-Journal) / Лёд и Снег
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Влияние метеорологических условий на формирование ледового режима Онежского озера
Get PDFThe formation of the ice regime on large lakes is mostly determined by the complex meteorological processes occurring over the water area. Previous studies of the air temperature influence on the ice regime formation on the Lake Onega were based on observational data on the state of the ice cover in the Petrozavodsk Bay, as well as the materials of the rare missions of aerial reconnaissance performed in the second half of the XX century. So, it was necessary to revise the previously established dependencies using the present-day satellite data for 2000-2018, and to determine the nature of influence of other meteorological factors, among which a thickness of the snow cover on the Lake area. The authors obtained regularities of changes in the characteristic dates (complete freeze-up – ±5 days/°C and final clearing of ice – ±3 days/°C) of the ice regime on the Lake Onega, depending on changes in the average air temperature that preceded these dates (autumn and spring) for the period of two months. The regression equations to calculate these dates on the basis of the previous three - and four-month periods from the data of 2000-2018 are also given. Relative to the above mentioned results for the previous period, a certain shift by a month ahead of two- and three- period exerting influence on the date of the complete freezeup is noted. Dependencies to calculate the cumulative daily temperatures for the period of the ice regime formation (the beginning of the formation of ice phenomena, complete freeze-up phase, the beginning of the breakup phase, clearing of the ice) were also deduced. Together with the data on the expected air temperature over the Lake these dates provide a potential possibility to estimate (predict) the characteristic dates of the ice regime. The significant influence of the average snow cover thickness on the process of destruction of the ice cover was shown, and the nature of the statistical relationship (along with the air temperature) was also determined.Установлены статистические взаимосвязи между метеорологическими параметрами (температура воздуха, снегонакопление) и характеристиками ледового режима Онежского озера за 2000–2018 гг. Приведены регрессионные уравнения для расчёта характерных дат ледового режима, а также сумм накопления положительных и отрицательных температур воздуха над его акваторией во время формирования ледяного покрова
Моделирование динамики приливного ледника Ханса (Шпицберген) на основе стохастической модели
Get PDFThe dynamics of the Hansbreen tidal glacier (Svalbard) is manifested at different time scales. In addition to the long-term trend, there are noticeable inter-annual fluctuations. And the last ones are precisely the subject of this work. Based on general conclusions of the theory of temporal dynamics of the massive inertial objects, the observed inter-annual changes in the length of the glacier can be explained as a result of the accumulation of anomalies of the heat fluxes and water flows. In spite the fact that the initial model of glacier dynamics is deterministically based on the physical law of conservation of ice mass (the so-called the «minimal model» was used), the model of length change is interpreted as stochastic. From this standpoint, it is the Langevin equation, which includes the effect of random temperature anomalies that can be interpreted as a white noise. From a mathematical point of view, this process is analogous to Brownian motion, i.e. the length of the Hansbreen glacier randomly fluctuates in the vicinity of its stable equilibrium position. Based on the Langevin equation, we passed to the Fokker–Planck equation, the solution of which allowed us to obtain the distribution function of the probabilities of interannual fluctuations of glacier length, which is close to the normal law. It was shown that the possible range of the variability covers the observed interval of the length fluctuations. The pdf is close to normal distribution.Для моделирования межгодовой динамики длины ледника Ханса на Шпицбергене использована «минимальная модель», интерпретируемая как стохастическое уравнение Ланжевена с переходом к уравнению Фоккера–Планка. Получена формула, выражающая дисперсию колебаний длины ледника в зависимости от его параметров. Сопоставление расчётов с данными наблюдений позволило получить хорошие результаты
Влияние оттепелей на снежный покров и промерзание грунта при современных изменениях климата
Get PDFThaw and liquid precipitation retard cooling of snow cover and soil surface and so may be a factor of heating. This slows down the soil freezing due to more active freezing of the wet snow, and, thus, promotes cooling and re-cooling of the soil. However, there are a number of factors which intensify the soil freezing after thaw. With thaw, the thickness of the snow cover decreases, and its density increases. In addition, after freezing wet snow improves the contact between the ice crystals, which increases the hardness and thermal conductivity of the snow. As a result, after the thaw, the thermal protection ability of the snow decreases, and this can accelerate freezing of the soil. The dynamics of snow accumulation in Russia is considered in the paper. Using data obtained in the Western Svalbard, we demonstrate the increase in the number of thaws and liquid precipitation and influence of them on the snow cover and soil freezing. The influence of thaw on the growth of thermal resistance of snow cover is also considered. Calculations have shown that in the absence of a thaw, the depth of soil freezing is 1.26 m. With a thaw lasting 10 days, which begins on the 40th day from the start of soil freezing, the depth of freezing is reduced down to 1.2 m without considering changes in snow cover. When taking into account changes in the thermal resistance of snow cover, the depth of soil freezing by the end of the cold period increases up to 1.32 cm. With a thaw in the mid-winter, i.e. on the 70th day, the depth of freezing decreases down to 1.22 m, that is smaller than the depth of freezing without thaw. This scenario is in accordance with changes in snow accumulation dynamics under the present-day climate, as in many areas most of the solid precipitation falls in the first half of the cold period. As a result, for a period after a thaw the smaller volume of snow will be deposited, and this will retard increasing in thermal resistance of the snow coverРассмотрено влияние климатических изменений на динамику снегонакопления, оттепели и жидкие осадки за холодный период на Западном Шпицбергене. На основе математического моделирования и численных экспериментов определена глубина промерзания грунта при формировании оттепели в разный период времени
О возможности реконструкции климатического сигнала в нарушенной записи изотопного состава древнего льда (0,4–1,2 млн лет назад) в керне станции Восток (Центральная Антарктида)
Get PDFIn this work we have presented new detailed (with the resolution of 10 cm) stable water isotope (δD and δ18O) profile measured in the central Antarctic Vostok ice core section that contains old ice with the age from 0.4 to 1.2 million years. To interpret these data we have developed a model of molecular diffusion in ice and determined the value of so-called «diffusion length». We have demonstrated that the climatic signal in this ice interval is disturbed by a combination of two processes, ice layer folding (that is accompanied by layer overturning and mixing) and molecular diffusion. The whole old ice interval can be divided in 5 zones that differ in terms of character and intensity of these two processes. In three of these zones the climatic signal is partly preserved and could be restored to some extent. However, in the most interesting and old zone 5 (0.75–1.2 Ma) the climatic signal is nearly completely erased and could hardly be reconstructed. At the same time, the isotopic records obtained from the Vostok old ice have preserved the information on the mean level of the isotopic content of ice in glacial and interglacial stages. This gives an opportunity to reveal and study long-term climatic trends with typical duration longer than main climatic cycles (40–100 ka).Представлены новые детальные данные (с разрешением 10 см) об изотопном составе (δD и δ18O) керна со станции Восток в интервале 3318–3537 м, содержащего древний лёд возрастом 0,4–1,2 млн лет. Показано, что климатический сигнал в этом интервале льда сильно искажён совместным действием стратиграфических нарушений в залегании ледяных слоёв и молекулярной диффузии. Сделана попытка частично восстановить климатический сигнал в отдельных интервалах древнего льда
Наледи бассейна р. Индигирка по современным снимкам Landsat и историческим данным
Get PDFThe paper presents methods and results of creation of the digital catalogue of aufeises for the Indigirka river basin made on the basis of Landsat images and historical data. The region under study is the basin before the hydrometric section of GMS Vorontsovo, its area is about 305 000 km2. Historical data were taken from the Inventory of naleds of the North-East of the USSR territory published in 1958 and topographic maps. It includes the estimated coordinates and characteristics of 897 aufeises with total area of 2064 km2. The Landsatbased identification of aufeises for 2013–2017 allowed making description of 1213 aufeises over a total area of 1287 km2. The integrated digital catalogue of the aufeises for the Indigirka river basin based on combination of the above two sources is available at https://issues.pangaea.de/browse/PDI-17699. 10% of the largest aufeises make up about 60% of the total area of all aufeises according to both sources. The largest number of aufeises is at altitudes of 900–1300 m. The interannual variability of area of the aufeises for the period 2001-2016 was estimated by the example of the Bolshaya Momskaya naled and the group of large aufeises in the basin of the Syuryukty River which is the left tributary of the Indigirka. The conclusions cannot be considered unambiguous due to certain limitations of the imagery data but the results of the analysis is indicative of a tendency to decreasing in the area of the Bolshaya Momskaya naled in recent years, while no reduction in the aufeis area is noted in the basin of the Syuryukty River. The main results of this work are the new geodatabase of the aufeises in the Indigirka river basin, and also the comparison of the satellite observations with historical data performed for two major naleds. It is established that the satellite-estimated total area of aufeises is 1.6 times less than in the Cadastre (1958). At the same time, it was found that more than 600 aufeises recognized by the Landsat images were absent in the Cadastre of 1958. This may suggest that either the Cadastre data is incomplete or that conditions of the aufeis can be significantly changed over the past 50 years.На основе Кадастра наледей Северо-Востока СССР (1958 г.) и топографических карт создана база данных о 897 наледях в бассейне р. Индигирка. По данным космической съёмки Landsat за 2013– 2017 гг. выявлены 1213 наледей суммарной площадью 1287 км2. Создан единый электронный Каталог наледей в бассейне р. Индигирка. Современная площадь наледей здесь в 1,6 раза меньше, чем по данным Кадастра 1958 г., но в Кадастре отсутствуют сведения более чем о 600 наледей, обнаруженных по снимкам.
Химический, изотопный и газовый состав однолетнего морского льда по данным кернов дрейфующих станций БАРНЕО за 2013-2015 гг.
Get PDFAs a result of the work performed at the BARNEO drifting stations (2013-2015 in the polar region of the Arctic ocean), a comprehensive testing was carried out and new data were obtained on the structure of one-year sea ice, its salinity, the distribution of ions of water-soluble salts, and the content of isotopes δ2H and δ18O within the ice thickness and snow falling on the ice surface. The composition of gas inclusions in the ice was also determined. The distribution of electrical conductivity across the ice thickness, determined by analysis of the cores with a length of 175-178 cm, is typical for such ice - it decreases from top to bottom with two maxima on the lower and upper boundaries of the ice. This is typical characteristic of the first-year sea-ice. Snow cover is characterized by a significant increase in electrical conductivity at the contact with the underlying ice. The chemical composition of the investigated ice-cores and the ratio between its components are similar to the composition of the sea water, although the concentrations of all components are lower than in the initial solution. The composition of gas inclusions in the ice does closely correspond to the atmospheric air, and it practically does not change in depth. The isotopic composition in the cores becomes heavier towards the bottom of the ice. This allows conclusion of a gradual decrease in the contribution of water with a light isotopic composition. The change in the isotopic composition along the ice depth, with the separation of zones with more light isotopes, reflects the changing temperature conditions of ice accumulation (with low isotopic fractionation at rapid freezing under the large temperature gradient) and regional features of the isotopic composition of sea waters in which the ice drift takes place. Salinization of the snow horizon lying on the ice surface provides a possibility of the sea salt transportation not only from surface of open water, but also from the surface of sea ice. This may be used for paleogeographic reconstructions in the Arctic using the analysis of the composition of massive vein ice.На дрейфующих станциях БАРНЕО-2013-2015 гг. в районе Северного полюса исследованы керны морских льдов, а также образцы льда, снежного покрова, подлёдной морской воды, определён состав газовых включений во льду. Получены новые данные о строении морского льда, его солёности, распределении ионов водно-растворимых солей и содержании изотопов δ2Н и δ18O в толще льда и снега, выпадающего на поверхность льда
Распределение холодного и тёплого льда в ледниках на Земле Норденшельда (Шпицберген) по данным наземного радиозондирования
Get PDFData of ground-based radio-echo sounding of 16 glaciers located on the Nordenskiold Land, Spitsbergen, carried out in springs of 1999, 2007 and 2010–2013, allowed defining five glaciers as of the cold thermal type while other eleven ones were polythermal glaciers. In the last ones (polythermal) the average thickness of the upper layer of cold ice and the bottom layer of temperate ice was equal to 11-66 m and 15-96 m, respectively. The ratio of these thicknesses varies from 0.32 to 2.28, and the volume fraction of temperate ice in the total volume of the glaciers varies from 1 to 74% and changes from 0 to 50% in the ablation zone up to 80% in the accumulation zone. Thickness of cold ice was determined by measured delay time of radar reflections from cold-temperate surface (CTS) while thickness of temperate ice was derived as a difference between the total thickness of the glacier and the thickness of its cold ice. For interpretation of radar reflections from CTS we used the noticeable distinction in character of the radar reflections from the upper and lower thicknesses of glacier: absence of internal reflections (excluding reflections from buried crevasses and glacier wells) from upper cold ice layer and a great number of reflections of hyperbolic form from the lower layer related to strong scattering of radio waves by water inclusions in the temperate ice. According to the measurements, relative power of the radar reflections from CTS is by 5,5–14,2 dB smaller than those from the bedrock, that can be considered as an indicator of smaller water content at CTS; so, the repeated measurements of their relative power can be used for estimation of temporal changes in the water content at these boundaries. In layers of the temperate ice, the series of vertical hyperbolic reflections penetrating the cold ice down to CTS and further to the bedrock were detected. Such reflections are related to buried crevasses and/or the glacier wells and can serve as sources of the water permeating during the melt periods from the glacier surface down to CTS and bedrock and, thus, influencing on the ice viscosity and fluidity as well as on velocity of the bottom sliding in the polythermal glaciers. Repeated measurements of relative power of reflections from buried crevasses and wells can also be used to study processes of freezing them through and emptying during the period before start of the surface melting. Relation between volume of temperate ice and area of 16 studied glaciers was used to estimate the probability of existence of polythermal glaciers with a temperate ice core in all 202 glaciers in the Nordenskiold Land. 72 glaciers with areas exceeding 1.79 km2 may be referred to the polythermal type. The probable total volume of temperate ice in these glaciers amounts roughly to 10 km3, and with the 95% confidence it is within the interval from 8 to 33 km3. Almost 80% of the whole temperate ice may be concentrated in only five glaciers with area more than 17 km2, that makes up 2.5% of the total number of glaciers and about 30% of their total area. Data presented in this paper demonstrate more sophisticated pattern of the cold and temperate ice distribution within the glaciers than it was earlier known that should be taken into consideration when modeling and forecasting dynamics of the polythermal glaciers and investigating internal processes of the temperate ice formation in such glaciers.По данным наземного радиозондирования 16 ледников в 1999, 2007 и 2010–2013 гг. на Земле Норденшельда установлено, что пять из них относятся к ледникам холодного типа, а 11 – к ледникам политермического типа с верхним слоем холодного льда cо средней толщиной 11–66 м и придонным слоем тёплого льда со средней толщиной 15–96 м. Около 80% всего тёплого льда сосредоточено в пяти ледниках площадью более 17 км2, которые составляют 2,5% общего числа ледников и около 30% всей их площади.
Оценка объёмной льдистости дисперсных грунтов Центрально-Якутской низменности по данным георадиолокации
Get PDFThe previously unknown dependence between the volume ice content of frozen dispersed soils and their radiophysical properties (the speed of propagation and specific attenuation of the amplitude of electromagnetic waves) was studied in the layer of annual heat flows of Central Yakutia. The correlation between these characteristics determined in the laboratory and the method of discrete georadiolocation is established. The peculiarity of the connection is the sharp decline in the sensitivity of the propagation speed and the specific attenuation of electromagnetic waves in frozen dispersed soils with high volume ice content (more than 60%). In general, the specific attenuation of electromagnetic waves is more responsive to the change in the volume of ice content of frozen dispersed soils and, thus, it is more preferable to solve the problem of quantitative evaluation of this characteristic. The proposed method of reusable measurements of signals of georadiolocation with changing position and azimuth of antennas of georadars in the vicinity of the network points of geological and geophysical observations allows to estimate the average values of the propagation speed and specific attenuation of electromagnetic waves with an error of not more than 10%. Due to this, according to the equations of logistic functions it is possible to calculate the average values of volume ice content with an error of 7–11%. With this error, the picture of the probability distribution according to the georadiolocation values of the volume ice content in the averages is completely identical to the laboratory data. On this basis, the found regression equations are recommended to be used for the calculation of the speed of propagation and specific attenuation of electromagnetic waves of background or average values of the volume ice content of frozen dispersed soils of the annual heat transfer layer in any part of the ice complex of the Central Yakut lowland. Установлена достаточно тесная корреляционная связь между объёмной льдистостью и радиофизическими свойствами мёрзлых дисперсных грунтов в слое годового теплооборота, позволяющая вычислить средние значения объёмной льдистости с ошибкой 7–11%. Это даёт возможность использовать предлагаемые уравнения регрессии для расчёта фоновых значений объёмной льдистости мёрзлых дисперсных грунтов по их радиофизическим свойствам в слое годовых теплооборотов
Роль гидрометеорологических факторов и солнечной активности в межгодовых изменениях площади льдов Восточно-Сибирского моря
Get PDFInterannual changes of the summer ice coverage were investigated, and the role of hydrometeorological factors and solar activity in long-period fluctuations of the ice area in the East Siberian Sea was determined. Multivariate statistical analysis of time series of the ice cover, hydrometeorological elements, and the solar activity (SA), was performed for the period from 1950 to 2012 with regard for the cross-correlations of the analyzed variables that made possible to develop the equations of interannual fluctuations of the ice coverage in the East Siberian Sea in August and September. The equations include the following variables: air temperature in June–August of the current year TVI‑VIII; the atmospheric circulation presented by indices of Arctic oscillation (Arctic Oscillation, AO), Arctic dipole (Arctic Dipole, AD), Pacific North American oscillation (Pacific North American Oscillation, PNA); average annual runoff of river waters into the Laptev and East Siberian seas (RivLES) with a time shift of one and two years; average annual index of the North Atlantic thermal state (AMO) with a time lag of eight years; solar activity SA, presented by the average annual Wolf number with advancing of one year. Diagnostic calculations of the ice area by the obtained equations using the actual values of the indices did show a good agreement between the actual and calculated values in August and September from 1950 to 2012. These equations were used to calculate contribution of each factor to the general dispersion of fluctuations of the ice coverage. The most important factors influencing the ice cover of the Sea in August and September are: the air temperature; the atmospheric circulation, presented by the Arctic Oscillation at the end of winter; and Atlantic waters which are characterized by AMO with a time lag of eight years. The role of other factors, i.e. summer atmospheric circulation, river runoff into the above seas, and 11-year cycle of solar activity were found to be equal to only 5–10% for each. Basing on these estimates, it has been concluded that the obtained statistical equations may be used as the diagnostic models of interannual changes in the ice coverage.Получены статистические уравнения межгодовых колебаний площади льдов Восточно-Сибирского моря в августе и сентябре. Рассчитан вклад каждого фактора в общую дисперсию колебаний ледовитости. К преобладающим факторам, влияющим на площадь льдов в эти месяцы, относятся: температура воздуха; Арктическое колебание в конце зимы; индекс теплового состояния Северной Атлантики. Вклад в общую дисперсию режима летней атмосферной циркуляции, речного стока, расхода вод через Берингов пролив и солнечной активности находится в пределах 5–10% для каждого фактора.
Влияние условий на контакте снег–почва на глубину её промерзания (по наблюдениям в Курской области)
Get PDFThe results of measurements of the ground freezing under a snow cover do not always agree with the calculations. The reason for this may be variability of thermal characteristics of the snow cover which properties depend on the landscape features. One of probable reasons may be also the incomplete contact between the snow cover and the soil. In autumn, the ground surface is usually covered with fallen leaves or withered grass. Estimates show that, in the presence of such layer on the soil surface, the air gap between snow and soil with the 1 cm thickness has a thermal protection capacity equal to the value of a 10‑centimeter thick layer of snow. Sometimes the presence of local gaps in the snow-soil interface can also be caused by other reason, for example, the spontaneous downfall of a depth hoar layer. The results of field measurements of snow cover characteristics, ground freezing depths and investigation of the contact conditions at the snow-soil interface carried out in different landscapes are presented. The results of mathematical modeling showed that when the air gap between snow and soil is taken into account the calculated values of depth of ground freezing are in a good agreement with data of the measurements. This consideration is especially important for small thicknesses of snow cover with high density and thermal conductivity. Numerical experiments did also show that the snow hardness is the necessary characteristic for analysis of the snow cover state. This provides more accurate estimating of the snow thermal conductivity that is closely connected with its hardness.Приводятся результаты полевых измерений параметров снежного покрова, глубины промерзания почвы и анализа условий на границе снег–почва в разных ландшафтах. Проведено сравнение данных измерений и расчётов по влиянию зазора на границе снег–почва на термический режим почвы и глубину промерзания. Изоляционный слой на границе снег–почва из растительности, опавших листьев и воздуха снижает поток тепла из почвы в атмосферу, что препятствует охлаждению грунта и уменьшает глубину его промерзания