Ice and Snow (E-Journal) / Лёд и Снег
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Определение снегозапасов Западной Сибири по расчётам на модели локального тепловлагообмена SPONSOR с использованием данных реанализа
Get PDFoai:oai.ice.elpub.ru:article/400Obtaining of reliable information about the characteristics of snow cover with high spatial and temporal resolution for large areas of Northern Eurasia, with rare or absent network of ground-based observations stations is an important and urgent task. Currently estimation of the value of the snow water equivalent (SWE) and the snow depth have a large degree of uncertainty, especially if we are moving from data at the point of observation stations to distributed space values. In this article, the simulations of SWE and the snow depth using Land-Surface Model (LSM) SPONSOR with input meteorological data taken from the ECMWF ERAInterim reanalysis was performed for Western Siberia for the period from 1979 to 2013. Fields of SWE and of the snow depth with high spatial and temporal resolution corresponding to the resolution of meteorological data of the ECMWF ERA-Interim reanalysis (time step of 6 hours, the grid resolution of 0.75° × 0.75° in latitude and longitude) were obtained. For the entire period SWE data were compared with observations, as simulated using the model and taken directly from the reanalysis ERA-Interim at points corresponding of observation stations. Also comparison of observations and satellite data of SWE for points of observation stations was performed. Correlation coefficients between observations and model and satellite data for SWE and the snow depth were calculated for the period from 1979 to 2013. These correlation coefficients between observations and results of simulations using LSM SPONSOR for SWE, and especially for the snow depth are the best of all methods. Maps with high spatial resolution for SWE, obtained by different methods, were constructed for February averaged. Comparing of constructed maps shows significant uncertainty of the SWE fields, besides field’s distortions are not evenly distributed across the region. It appears that no one of these methods currently can be used as a reference (unique) to determine SWE in the absence of data of ground-based observations. Overall, model simulations using LSM SPONSOR somewhat overstate SWE, however, this overestimation is not more than 10–20% for most part of the territory, except in the South. Model data are reasonably well reproduce SWE for Central, Eastern and, most probably, for Northern parts of the region, differing from a real at 10–15%. Data from used satellite archive a few underestimate of SWE. SWE data taken directly from the reanalysis ERA-Interim, give large distortions of the SWE field: these values for Northern parts of the region, are likely greatly underestimated, and for Western and Eastern parts of the region – inflated. It is shown that in general, the method of simulation of snow cover characteristics using LSM SPONSOR with input data taken from the ECMWF ERA-Interim reanalysis gives good results for the region of Western Siberia.Для территории Западной Сибири за период с 1979 по 2013 г. проведены расчёты снегозапасов и толщины снежного покрова с помощью модели локального тепловлагообмена SPONSOR с входными метеоданными, взятыми из реанализа ECMWF ERA-Interim. Показано, что коэффициенты корреляции между данными наблюдений и результатами численных расчётов на модели SPONSOR – наилучшие из всех методов. С помощью модели SPONSOR достаточно хорошо воспроизводятся данные снегозапасов по центральной, восточной и, наиболее вероятно, северной частям Западной Сибири
Текстура и структура подземных льдов позднего голоцена севера Западной Сибири
Get PDFThe Late Holocene ground ices are occurred due to freeze cracking, slope, thermocast, thermoerosion pro‑ cesses. New formation ice within may intervene to the Pleistocene, lower Holocene ground ice and perma‑ frost and can really complicate their structure. Relationship between seasonal and perennial new formation of ice with massive ice and permafrost was studied in cross section of the North Western Siberia. The features of texture and structure of ice formed in the thawing cavities, some cracks were determined. The differences in structure of the late Holocene ground ices and ground ices of the early Holocene and late Pleistocene were defined. The differences in ground ice texture and structure depend to the cavity configuration of the freezing and cracks and freezing temperature conditions. The quantitative parameters of the crystal structure can be used to identify closed‑cavity ice and crack ice in the composition of massive ice and determine mechanisms and conditions of formation before the Holocene ice wedges.В разрезах севера Западной Сибири изучено соотношение новообразований льда с залежеобразую щими льдами и мёрзлыми отложениями. Определены особенности текстуры и структуры льдов, сформированных в полостях протаивания, трещинах отседания и трещинах в тыловой части оползневых блоков мёрзлых пород. Установлены отличия структуры подземных льдов позднего голоцена от подземных льдов раннего голоцена и позднего плейстоцена
Использование наземных и спутниковых данных о снежном покрове для прогноза стока реки Нарын
Get PDFThe main source of river nourishment in arid regions of Central Asia is the melting of seasonal snow accu‑ mulated in mountains during the cold period. In this study, we analyzed data on seasonal snow cover by ground‑based observations from Kyrgyzhydromet network, as well as from MODIS satellite imagery for the period of 2000–2015. This information was used to compile the forecast methods of water availability of snow‑ice and ice‑snow fed rivers for the vegetation period. The Naryn river basin was chosen as a study area which is the main tributary of Syrdarya River and belongs to the Aral Sea basin. The representative mete‑ orological stations with ground‑based observations of snow cover were identified and regression analysis between mean discharge for the vegetation period and number of snow covered days, maximum snow depth based on in‑situ data as well as snow cover area based on MODIS images was conducted. Based on this infor‑ mation, equations are derived for seasonal water availability forecasting using multiple linear regression anal‑ ysis. Proposed equations have high correlation coefficients (R = 0.89÷0.92 and and fore‑ casting accuracy. The methodology was implemented in Kyrgyzhydromet and is used for forecasting of water availability in Naryn basin and water inflow into Toktogul Reservoir.Проанализированы данные о сезонном снежном покрове за 2000–2015 гг. на основе спутниковых снимков MODIS и наземных наблюдений на шести метеостанциях: Тянь-Шань, Нарын, Ит-Агар, Чаек, Тюя-Ашуу и Суусамыр. Данные MODIS использованы для определения доли площади в бассейнах притоков Нарына. Расчёт водности рек на период половодья выполнен на основе анализа снежного покрова по наземным и спутниковым данным
Вариации скорости снегонакопления в Центральной Антарктиде за последние 250 лет
Get PDFThe present-day global climate changes, very likely caused by anthropogenic activity, may potentially present a serious threat to the whole human civilization in a near future. In order to develop a plan of measures aimed at elimination of these threats and adaptation to these undesirable changes, one should deeply understand the mechanism of past and present (and thus, future) climatic changes of our planet. In this study we compare the present-day data of instrumental observations of the air temperature and snow accumulation rate performed in Central Antarctica (the Vostok station) with the reconstructed paleogeographic data on a variability of these parameters in the past. First of all, the Vostok station is shown to be differing from other East Antarctic stations due to relatively higher rate of warming (1.6 °C per 100 years) since 1958. At the same time, according to paleogeographic data, from the late eighteenth century to early twenty-first one the total warming amounted to about 1 °C, which is consistent with data from other Antarctic regions. So, we can make a conclusion with high probability that the 30-year period of 1985–2015 was the warmest over the last 2.5 centuries. As for the snow accumulation rate, the paleogeographic data on this contain a certain part of noise that does not allow reliable concluding. However, we found a statistically significant relationship between the rate of snow accumulation and air temperature. This means that with further rise of temperature in Central Antarctica, the rate of solid precipitation accumulation will increase there, thus partially compensating increasing of the sea level.Современные изменения температуры воздуха и скорости накопления снега, полученные инструментальным путём на антарктической станции Восток, сопоставлены с палеоклиматическими реконструкциями за последние 250 лет. Показано, что период 1985–2015 гг., вероятно, был самым тёплым 30-летием за последние 2,5 века. Скорость снегонакопления положительно коррелирует с изменчивостью температуры воздуха – это показывает, что повышение температуры в будущем будет сопровождаться ростом количества снега, накапливаемого в Антарктиде, что частично скомпенсирует рост уровня Мирового океана. Вместе с ростом температуры воздуха на протяжении последних 50 лет имело место и увеличение количества осадков, однако являются ли современные значения скорости снегонакопления аномальными для последних 250 лет на основании имеющихся данных сказать трудно
Скорость распространения радиоволн в сухом и влажном снежном покрове
Get PDFIn recent years, ground-penetrating radars are widely used for measuring thickness and liquid water content in snow cover on land and glaciers. The measurement accuracy depends on radio wave velocity (RWV) adopted for calculations. The RWV depends mainly on density, water content and structure of the snow cover and ice layers in it. The density and wetness of snow, and its structure can be estimated from data on RWV, using the available experimental and theoretical relations. Satisfactory results can be obtained using the Looyenga’s (1965) equations to estimate the density and wetness of snow cover, and equations of van Beek’s (1967) showing the distinction between RWV speeds velocities in snow cover and ice layers with different prevailing orientation and sizes of air or water inclusions.RWV in dry snow with density 300 kg/m3 may vary by 32 m/µs, depending on whether the vertical or horizontal orientation of the air inclusions prevails therein. In ice with density 700 kg/m3 effect of air inclusions orientation on differences in RWV is reduced to 5 m/µs. If the inclusions are not filled with air but with water, the difference in RWV in snow is 21 m/µs, and in ice is 24 m/µs. The RWV is affected not only by orientation of the inclusions, but their elongation. Twofold elongation of ellipsoidal air and water inclusions increases the difference in RWV in snow (with a density 300 kg/m3 ) to 23 m/µs and 22 m/µs.These estimates show a noticeable influence of snow structure on RWV in snow cover. The reliability of the above RWV estimates depends significantly on a thermal state of the snow cover, and decreases during snowmelt and increases in the cold period. It strongly depends on accuracy of measurements of the RWV in snow cover and its separate layers. With sufficiently high accuracy of the measurements this makes possible to detect and identify loose layers of deep hoar and compact layers of infiltration and superimposed ice, which is important for studying the liquid water storage of snow cover and a glacier mass balance. Therefore, considerable attention should be given to accuracy of the RWV measurements in dry and wet snow cover and its individual layers. With sufficiently high accuracy of measurements of the RWV, this should allow revealing such layers and estimating their thickness and average density.Представлены результаты расчётов скорости распространения радиоволн в снежном покрове в зависимости от плотности, влажности, структуры снега и прослоек в нём льда по разным эмпирическим и теоретическим зависимостям. Различие в скорости распространения радиоволн в сухом снеге плотностью 300 кг/м3 с преобладающей вертикальной или горизонтальной ориентацией включений воздуха достигает 32 м/мкс и уменьшается до 5 м/мкс во льду плотностью 700 кг/м3. Выполненные оценки показывают заметное влияние структуры на скорость распространения радиоволн в сухом и влажном снежном покрове, что позволяет обнаруживать и идентифицировать рыхлые слои глубинной изморози и плотные слои инфильтрационного и наложенного льда
О наступании ледников в условиях вулканической деятельности вулкана Ключевской (Камчатка)
Get PDFNew data on continuing advance of the Kamchatka glaciers Erman, Vlodavets, Sopochny, Schmidt, and Bogdanovich were obtained as a result of analysis of aerospace information taken at different times. Glacier Erman advances during the past 70 years (1945–2016). Over the period from 1949 to 2016, its area increased by 4.7 km2 and the length – by 3.3 km (from 18.2 to 21.5 km). The highest speed of advancing had been estimated for the Schmidt glacier, in 2007–2013 it exceeded 100 m/year. We had identified a new isolated glacier between glaciers Erman and Schmidt, named as the Obvalny (the «Avalanche») glacier, since in 1945 this glacier was buried under volcanic-avalanche deposits resulted from the Klyuchevskaya volcano eruption. In 1975–2016, the Obvalny glacier advanced over a distance of about 1700 m. Also, we had found more 30 ice-rock massifs («wandering glaciers») on slopes of the Klyuchevskaya volcano. Their contours looked like drops or tongues, and some of them advanced in the frontal zone. From 2002 to 2016, the «wandering glacier» in the upper reaches of river Glubokaya (eastern sector of the volcano) advanced for 740 m (55 m/year). Advancing of glaciers here is a consequence of lateral and terminal eruptions of the Klyuchevskaya volcano in XX and XXI centuries. Erman Glacier, glacier advance, Klyuchevskaya volcano, lateral eruption, space images, volcanic and rock avalanche deposits, «wandering glaciers».На основе анализа разновременной аэрокосмической информации за период 1949–2016 гг. полу- чены новые данные о современном состоянии и наступании ледников района вулкана Ключев- ской – Эрмана, Влодавца, Сопочного, Шмидта, Богдановича и безымянных «блуждающих ледников». Площадь ледника Эрмана увеличилась на 4,7 км2, а длина достигла 21,5 км. Самые высокие темпы наступания – до 100 м/год – характерны для ледника Шмидта. Наступание ледников есть следствие латеральных и терминальных извержений вулкана Ключевской в XX и XXI вв
Эволюция климата, оледенения и подледниковой среды Антарктиды по данным исследований ледяных кернов и проб воды озера Восток (Основные итоги работ по проекту РНФ, 2014–2016 гг.)
Get PDFWork on the project focused on the following five areas: 1) field works in Antarctica at Vostok and Concordia stations; 2) experimental and theoretical studies in the field of ice core and paleoclimate research; 3) experimental and theoretical works related to the exploration of subglacial Lake Vostok; 4) development of technology and drilling equipment for deep ice coring and exploration of subglacial lakes; 5) upgrading the analytical instrumentation in the Climate and Environmental Research Laboratory (CERL) of the Arctic and Antarctic Research Institute. The main achievements in the field of ice core and paleoclimate research include 1) further elaboration of a new method of ice core dating, which is based on the link between air content of ice and local insolation, 2) investigation of the possible applications of the 17O-excess measurements in ice core to the paleoclimate research, 3) a better understanding of the mechanisms of the formation of relief-related variations in the isotopic content of an ice core drilled in the area of Antarctic megadunes, and 4) obtaining the first reliable data set on the variations of the 17O-excess in the Vostok core corresponding to marine isotope stage 11. As part of our studies of subglacial Lake Vostok, we have obtained a large body of new experimental data from the new ice core recovered from the 5G-3 borehole to the surface of the subglacial lake. Stacked profiles of isotopic composition, gas content and the size and orientation of the ice crystals in the lake ice have been composed from the data of three replicate cores from boreholes 5G-1, 5G-2 and 5G-3. The study reveals that the concentration of gases in the lake water beneath Vostok is unexpectedly low. A clear signature of the melt water in the surface layer of the lake, which is subject to refreezing on the icy ceiling of Lake Vostok, has been discerned in the three different properties of the accreted ice (the ice texture, the isotopic and gas content of the ice). These sets of data indicate in concert that poor mixing of the melt (and hydrothermal) water with the resident lake water and pronounced spatial and/or temporal variability of local hydrological conditions are likely to be the characteristics of the southern end of the lake. A considerable part of the funding allocated by the RSF to this project was used for upgrading the analytical instrumentation for ice core studies in the CERL of AARI. Using this grant, we purchased and started working with the Picarro L-2140i, a new-generation laser mass analyzer, and set the upgraded mass spectrometer Delta V Plus into operation. The new equipment was used to carry out research planned as part of the project, including the setting up and carrying out of new measurements of 17О in ice cores.Изложены основные результаты работ, выполненных Лабораторией изменений климата и окружающей среды ААНИИ по проекту Российского научного фонда в 2014–2016 гг. Показано, что поддержка фонда способствовала получению научных результатов международного уровня в двух приоритетных направлениях антарктических исследований – реконструкции палеоклимата по ледяным кернам и изучении подледниковой среды Антарктиды
История Cкандинавского ледникового покрова и окружающих ландшафтов в валдайскую ледниковую эпоху и начале голоцена
Get PDFThe reconstruction of natural environments associated with the development and degradation of the Scandinavian Ice Sheet from the Mikulino Interglacial period to the Holocene is presented in this paper. A diagram showing the change of vegetation in the periglacial zone of the Ice Sheet during the last 130 ka had been constructed from the results of studying the key sections with glacial and interstadial deposits in North-Western areas of the East European plain. In addition, paleolandscape maps (glacier, vegetation, periglacial basins) were composed for Fennoscandia and adjacent areas for the following time periods: the Last Glacial Maximum (time of maximum cold or a minimum of heat provision), the Late Glacial time (optimum of the Allerød interstadial, the maximal cooling and the ice advance of the Late Dryas), and the Early Holocene (the Preboreal). The maps for the Late Glacial time show the most dramatic changes of the main components of paleolandscape associated with positions of the ice margin and the nature of the proglacial drainage. Changes in the glacial structures of the Scandinavian Ice Sheet during the growth of the warming were happening faster, mainly due to local factors (topography of the glacier bed, tectonics, and glacioisostatic and glacioeustatic movements). In the vegetation of the periglacial zone, the composition of flora throughout the late Pleistocene remained unchanged, although structures of the plant communities varied. This vegetation consisted of a mix of forest, tundra and steppe complexes adapted to the sharply continental climate conditions. Transition from the Late Dryas to the Early Holocene was found everywhere in the changes of the plant communities, that could be considered as the initial stage of formation of the present-day latitudinal zonation.Рассматриваются вопросы изменения структуры растительных сообществ приледниковой зоны от конца микулинского (эемского) межледниковья до начала голоцена. Установлена зависимость структуры растительного покрова от темпов распространения и деградации Скандинавского ледника. По итогам изучения 118 опорных разрезов с ледниковыми и межстадиальными отложениями построена схема изменения растительности в приледниковой зоне за последние 130 тыс. лет для северо-западных районов Восточно-Европейской равнины. Наибольшее внимание уделено последнему ледниковому максимуму, аллерёду, позднему дриасу и началу голоцена (пребореалу)
Новейшие данные об оледенении северного склона массива Таван-Богдо-Ола (Алтай)
Get PDFAs of 2015, 16 glaciers, their total area 23.46 km2 and the weighted-mean altitude of the firn line 3335 m, were isolated on the Northern slope of the of the Tavan-Bogdo-Ola massif (Altai) on the basis of field studies and analysis of satellite images (Landsat-7, SPOT-5, Geoeye-1, CARTOSAT-1). The differences in elevation of the firn lines on the West and East of the investigated area reach 460 m, while the intensity of glaciation differs in 2 times due to changes of annual precipitation from 360 mm in the East to 880 mm in the West. Data on the glaciation had been improved and complemented for three time sections: 1962, 2001, and 2009. Since 1962, areas of the glaciers decreased by 24.3%. The largest rates of the glacial area decreasing took place in 2001–2009. Degradation of the upper parts of the glaciers and uncovered ice-dividing rocks played the major role in the process of retreating. In 2009–2015, the intensity of shortening of the glaciers decreased, and the degradation of their upper parts stopped. In 2000–2009, mainly small glaciers degraded. After 2009, small glaciers have slowed the decline with simultaneous increase of retreating of tongues of the valley glaciers. Abrupt (280 m) shortening of tongue was observed on the glacier Argamdgi-2-Western. This behavior of glacier could be caused by different rate of response to the dramatic warming within the period 1985–2000 and climate stabilization after 2000. If the climatic trends of the last 15 years will be the same in the coming years, we should expect continued rapid retreat of the tongues of the two largest glaciers of this massif along with the further slowdown of the retreat of small glaciers.На основе многолетних полевых наблюдений, дешифрирования космических и аэрофотоснимков уточнены и дополнены данные по современному (2015 г.) оледенению северного склона массива Таван-Богдо-Ола (каталоги и карты ледников), оценено его состояние на 1962, 2001 и 2009 гг. Проанализированы скорости и механизмы сокращения ледников с 1962 по 2015 г. Установлены современное замедление отступания малых ледников и возрастание скоростей отступания относительно крупных ледников
О возможности использования методов дистанционного зондирования Земли при расчётах гляциологических показателей для горных районов Узбекистана
Get PDFThe ALOS/AVNIR-2 satellite data (2007–2010) allowed estimating areas of glaciers, change in the areas for 50 years, and the number and areas of new naturally-dammed lakes in the mountain regions of Uzbekistan. Boundaries of these gla‑ ciers together with the ALOS/PALSAR data (2010) were used as the basis to determine position of the firn line. It was revealed that since 1980s elevation range of the line gradually decreased. The relationship between average elevation of the firn line and the upper limit of the juniper tree occurrence as well as changing of this relation since 1980s are consid‑ ered. The revealed lakes served as the basis for verification of probabilistic model of the moraine-dammed lake forma‑ tions due to the glacier recessions in the basins under consideration. It was shown that the GIS-techniques based on the use of this model together with data on glaciation and the relief digital model may significantly simplify searching of new lakes. Application of a system of the mudflow movement modeling makes possible to estimate a risk level in a case of a lake bursting. Current information about changing elevations of the glacier surfaces was obtained duet to the radar inter‑ ferometry and the altimeter data. The digital model of the river Pskem upper course (the DEM) had been built using the satellite TerraSAR‑X/TanDEM‑X data (2011–2012). All datasets of the elevations were checked for horizontal shifts of the relief digital models relative to the ICESat profiles (2003–2008). Evaluation of accuracy and morphological analysis of all the relief models for the investigated region were also made. DEMs differencing, the difference between ICESat measure‑ ments and DEM, nearby ICESat footprints within one track and between the tracks were carried out to assess the change in elevations of the glacier surfaces. Average rate of the surface lowering of an individual glacier with the maximal number of footprints (7) in the track is equal to −1 m/year; on average for 7 corrie-valley glaciers with northern/north-eastern exposition, it is −1.3 m/year in the ablation zone. This rate increases toward to the glacier terminus. Average local mass balance in the ablation zone of the Barkrak Glacier is egual to −0.82±0.36 m w.e. a−1 for the period since 2000 till 2012.Рассматриваются вопросы использования спутниковой информации для решения нескольких задач: расчёта площади ледников Республики Узбекистан и скорости понижения их поверхности; поиска связи между высотой фирновой линии и верхней границей арчи; применения модели возможного формирования моренных озёр при отступании ледников и модели движения селевого потока в случае прорыва ледниковых озёр