Ice and Snow (E-Journal) / Лёд и Снег
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Изотопный состав кислорода и водорода повторно-жильных льдов Центрального Ямала
Get PDFNew data on the distribution of the isotopes δ18О and δD of ice wedges in Central Yamal are presented. In the summer of 2019, the massive wedge ice was studied in the thermal circus of the third marine terrace. On the surface of the terrace, polygonal-vein relief is common with a polygon size of about 10–20 m. The largest ice wedge № 1 in the upper part was 1.5 m wide, and its visible depth in the outcrop amounted to 2.3 m. Perpendicular to this wedge, another one № 2 was opened with a width of 60 cm, and 20 m from them the wedge № 3 was opened along the strike. At the level of the head of the wedge № 1, radiocarbon AMS dating was performed based on a sample of host deposits, which showed that the ice in the upper part was about 13 thousand years old (the ice age was of 13.6 cal. BP). According to the isotopic characteristics (average values of δ18О = −24.8, and δD = −187.6 ‰), the ice corresponds to the Yamal ice-wedge ice, which was formed during the MIS‑2 isotopic stage (the end of the Late Pleistocene). The isotopic composition of oxygen indicates temperatures of the cold period of the vein formation from −22.8 to −26.8 °C (on average 7 °C colder than the present-day) and the January temperatures from −34.2 to −40.2 °C (on average 10 °C colder than the present-day). For some ice samples (11 out of 43), high values of deuterium excesses (dexc = 12÷17 ‰) were observed, which is unusual for this type of ice. A few examples of high dexc values of ice wedges are mentioned in the literature for sections of Seyakha yedoma, Cape Sabler and Bolshoi Lyakhovsky Island, and note that for the ice dated to the Late Pleistocene. The deuterium excess values may reflect the unstable climatic conditions of the Late Pleistocene associated with changes in the vapor source and the trajectories of the air masses over the continent.Приведены новые данные о распределении δ18О и δD в повторно-жильном льду Центрального Ямала. По своим изотопным характеристикам (средние значения δ18О = −24,8, а δD = −187,6 ‰) лёд соответствует жильным льдам Ямала, которые формировались в изотопную стадию МИС‑2 (конец позднего плейстоцена). Для некоторых образцов льда отмечены высокие значения дейтериевого эксцесса (dexc = 12÷17 ‰), что нехарактерно для этого типа льдов. Немногочисленные свидетельства высоких значений dexc в позднеплейстоценовом жильном льду описаны в литературе для раз‑ резов р. Сеяха, мыса Саблера и о. Большой Ляховский
Оценки современных изменений снегозапасов в бассейне Северной Двины по данным наблюдений и моделирования
Get PDFThe variability of snow accumulation in the Northern Dvina River basin at the end of March 1980-2016 was studied using data on the snow water equivalent of (SWE) obtained from archives of the Russian Institute of HydroMeteorological Information-World Data Center (RIHMI-WCD) as well as calculated by models of the local heat and moisture exchange SWAP and SPONSOR using the WATCH reanalysis (WFDEI) as input data. A possibility to use the SWE data from these sources to describe long-term variability of the SWE values, including trend, high-frequency component, quasi-decadal fluctuations, and spatial distribution, is evaluated. When describing the structure of the SWE variability, in particular, the contribution of trend and quasi-decadal fluctuations, as well as spatial characteristics, uncertainty remains associated with both the capabilities of the models under consideration and the imperfection of the observation network (insufficient density, measurement errors, etc.). Taking into account these uncertainties, the following conclusions can be made: the SWE variability in the Northern Dvina basin at the end of March has a low-frequency component (trend), as well as high-frequency, two- and five-year quasi-periodicities and quasi-decadal fluctuations. Long-lasting SWE anomalies in 1989–1995 and 1999–2005 and the absolute minimum in 1996 associated with quasi-decadal fluctuations are almost synchronously reflected in spring runoff anomalies. The informativeness of the considered data was also investigated from the point of view of the influence of SWE on the anomalies of the spring runoff of the Northern Dvina. The results of regression estimates and calculations of predictive values point to the advantage of the model SWE data for describing anomalies of spring river discharge compared to observations, which is primarily due to the high resolution of the model data. All the considered data sources indicate a long period of SWE deficits, starting from 2005 – 15-20%. Estimates of trend parameters are in a wide range. Depending on the data source, the rate of the SWE decrease over the basin, can vary from 4 mm per 10 years according to observations and up to 10 mm per 10 years according to calculations using the SPONSOR model.Изменчивость снегозапасов в бассейне р. Северная Двина (1980–2016 гг.) исследуется на основе данных о водном эквиваленте снега (ВЭС), полученных из станционных наблюдений и в результате расчётов на моделях тепло- и влагообмена. Обсуждаются оценки параметров тренда и вклада высокочастотных и квазидесятилетних колебаний, а также особенности пространственного распределения изменчивости ВЭС, полученные по сведениям из разных источников. В качестве критерия информативности наблюдений и модельных расчётов рассматриваются оценки вклада изменчивости ВЭС в конце марта в аномалии весеннего стока
Визуализация структурно-текстурных изменений в новообразующемся снежном слое при длительном снегопаде
Get PDFObservations were made on the dynamics of structural and textural transformations in the newly fallen snow layer during its transition to a stratigraphically significant snow accumulation layer. To visualize the structural and textural transformations during a prolonged snowfall and post-sedimentation changes in it after the snowfall stopped, a reflective screen was used in combination with photomicrography of solid precipitation and snow grains. Observations were made for seven days. Already on the third day, with the thickness of the newly formed snow layer of 12 cm, the primary texture in the form of internal layering, due to the microstructure of freshly fallen snow, began to differ in it. In the process of post-sedimentation transformations, the primary stratification in the newly formed stratigraphically significant snow layer was preserved, but became less noticeable. Micrographs showed that the deposited snowflakes were transformed by sublimation metamorphism to form small rounded RGsr particles, which differed little from the snow grains in the underlying layer. It is assumed that the structural and textural post-sedimentation transformations of solid precipitation in the upper part of the snow thickness are more controlled by the depth of penetration of the air temperature gradient. Lower boundary of this upper part is well distinguished in the snow profile owing to the optical anisotropy of the snow horizons composed of RGsr snow grains and FCso and DHla facet crystals. The performed studies demonstrated that the light-reflecting screen can be used in snow science as a simple tool for optical monitoring of structural heterogeneities of seasonal snow cover and visualization of post-sedimentation processes that occur during its growth.На примере наблюдений нарастания снежной толщи во время длительного снегопада охарактеризованы особенности проявления структурно-текстурных неоднородностей в новообразующемся снежном слое по диффузному отражению света в оптическом диапазоне спектра. Показана область практического приложения оптической диагностики в видимом диапазоне спектра при изучении стратиграфии снежного покрова
Строение снежного покрова на северо-востоке Московской области
Get PDFSnow stratigraphy can be considered as an integral characteristic of weather conditions of the corresponding winter season. The stratigraphic approach is convenient for a comparative analysis of the snow stratigraphy at different spatial-temporal scales, including the variability of the snow cover due to climate change. The snow stratigraphy can be sufficiently modeled on the basis of three meteorological characteristics: air temperature, wind speed and precipitation. Consequently, significant differences in the winter meteorological conditions should produce different stratigraphy.In the Moscow region winter temperatures are almost three degrees higher in the 21‑st century compared to the middle of the 20th century, though precipitation and wind speed are similar. Thus, changes in the snow stratigraphy can be expected. Comparative analysis of the results of stratigraphic studies carried out in the mid‑1950s to 1960s and 2010s indicates a slight decrease in the proportion of faceted crystal and depth hoar layers and increase in melt-freeze layers during the last decade, while the proportion of settled layers composed by rounded grains remains relatively invariable. However, the interannual variability of the winter weather produces higher variability in the snow structure compared to the expected effect of the long-term climate trends. The spatial distribution of the melt-freeze layers in the 2014–2019 was different compared to 1957/58 and 1961/62 due to the increase in the number and intensity of thaws in the winter seasons. In the 2010s, the number and thickness of ice crusts and melt-freeze layers increased in the middle part of the strata, which usually forms in January–February. Such layers composed 5 to 31% (17% in average) in 2014–2019 winters, while in 1957/58 and 1961/62 it was 7 and 10% respectively. A further increase in winter temperatures can enhance changes in snow stratigraphy and properties. It may result in thicker melt-freeze layers, weaker kinetic growth and shorter winter seasons.Представлены результаты исследования строения снежной толщи, выполненные в 2014–2019 гг. на северо-востоке Московской области на открытом незалесённом участке в периоды максимальных снегозапасов. Проведено сравнение полученных данных с результатами исследований снежной толщи, выполненными в том же районе А.Н. Формозовым и А.П. Павловым в 1950–60‑х годах. Установлено, что строение снежной толщи в 1957/58 и 1961/62 гг., считающихся типичными для исследуемой территории, отличается от строения в 2014–2019 гг., что может быть обусловлено увеличением зимних температур воздуха, а также числа и интенсивности оттепелей во второй половине XX – начале XXI в. При этом сохраняется большая межгодовая изменчивость зимних погодных условий, влияние которой на строение снежной толщи оказывается бóльшим, чем влияние многолетних трендов
Шесть десятилетий радиолокационных и сейсмических исследований в Антарктиде
Get PDFAntarctica was discovered by the First Russian Antarctic expedition in 1820. Subsequent studies were mainly descriptive in nature, and measurements were few in number. Only from the end of the 19th century systematic scientific observations were started in Antarctica. The first stage of studying the continent was completed in the middle of the 20th century, when the coastline was completely mapped and inland studies were carried on. The First International Geophysical Year (1957–1958) marked the beginning of systematic geophysical researches in Antarctica. Russia (USSR) took an active part in the work, opening Mirny and Pionerskaya stations in 1956. At the same time, seismic sounding, first conducted by the R. Byrd's expedition in 1933–1935, began to be carried out in Antarctica. In the first two decades after the International Geophysical Year, international scientific communities carried out the first comprehensive multidisciplinary research; a network of permanent year-round scientific stations was created, and a new method of radar sounding was introduced into the practice of work. The results of this stage are presented in the two-volume Atlas of Antarctica, published in the USSR. In the 1970s and 90s, most of the continent was covered by complex airborne geophysical surveys. The huge amount of accumulated data has been combined for generalization them into a single database within the framework of the International Bedmap project. Recent studies are mainly focused in unexplored areas of Antarctica, which by now are actually absent. Further accumulation of data promoted the two subsequent generations of the Bedmap project - Bedmap2 and Bedmap3. The use of GPR methods since the late 1990s has allowed us to study the structure of the snow-firn thickness at a new scientific and technical level, as well as to perform important engineering surveys aimed at ensuring the safety of transport operations in Antarctica. Currently, Russian research is focused on the study of the subglacial Lake Vostok and airborne geophysical works in the sector of 60°–100° E.Представлен обзор отечественных и зарубежных радиолокационных, георадарных и сейсмических исследований в Антарктиде за период с середины XX в. по настоящее время. В работу включён небольшой обзор более ранних экспедиционных работ. Отдельно рассматриваются вопросы исследований подледникового озера Восток и операции «Эймери». Приводятся схемы изученности, даётся характеристика сейсмической и радиолокационной аппаратуры, а также геодезических приборов, используемых для планово-высотной привязки отечественных работ
Глобальные гляциологические модели: новый этап в развитии методов прогнозирования эволюции ледников. Часть 1. Общий подход и архитектура моделей
Get PDFFor several decades, mathematical models of mountain glaciers and ice sheets have been used to study the dynamics of the cryosphere. In recent years, a new step in glaciological modeling has made possible to recon- struct processes in mountain-glacial systems both regionally and globally. The proposed review analyses rea- sons to use this possibility for global glaciological models, key assumptions and methods, general approaches and differences between individual models. Global glacier modeling is a rapidly developing field. This became possible only after the data on all glaciers of the world appeared in the Randolph Glacier Inventory in 2012. The ice thickness inversion procedures discussed in this review made it possible to calculate the initial volume and geometry of glaciers. Methods of varying complexity were used to regionalize global climate data and cal- culate glacier mass balance. Modeling the dynamics of glaciers required the adaptation of simplified schemes to represent the fluidity of ice (or the flow of ice). To date, only two global glacier models contain ice dynamics calculations based on Glenn's law and the diffusion equation: OGGM and GloGEMflow. Simulation results are subject to uncertainties due to input errors, climate predictions, model approximations, and calibration proce- dures. A new stage in the development of methods opens up opportunities to use a number of new directions in the study of the mechanisms that control the evolution of glaciation, depending on the implementation of a particular climatic scenario. Global glacier models make possible to build glaciological projections, calculate potential changes in the regime of glacial runoff, as well as assess risks and predict the occurrence of dangerous processes caused by changes in glaciation parameters, such as mudflows, landslides, and glacial lake outbursts.В обзоре рассмотрены предпосылки возникновения глобальных гляциологических моделей, ключевые допущения и методы, общие подходы и различия между отдельными моделями. Глобальные модели ледников позволяют строить гляциологические проекции, рассчитывать потенциальные изменения в режиме ледникового стока, а также оценивать риски и прогнозировать возникновение опасных процессов (сели, оползни, прорывы ледниковых озер), обусловленных изменениями параметров оледенения
Многолетние изменения ледовитости в районе архипелагов Шпицберген и Земля Франца-Иосифа
Get PDFA comparative analysis of inter-annual changes in ice coverage and time scales of its variability in the waters surrounding the Svalbard and Franz Josef Land archipelagos has been performed. The analysis was carried out for the selected quasi-homogeneous regions. Open sources of information (satellite observations) collected by the Arctic and Antarctic Research Institute were used. Seasonal and inter-annual changes in ice coverage were studied over the period 1979–2019, since the uniform series of the satellite data were available for this period. The change of a relatively stable type of ice regime to a regime with a high level of inter-annual variability, which occurred in 2004–2006, was established. A significant negative trend in the change in ice coverage, characteristic of the waters surrounding both archipelagos, was revealed. Correlation and spectral analyses were used to estimate possible periods of cyclic fluctuations in ice coverage (taking into account the limited duration of the observation series), which amounted about 5–6 years. An efforts were made to establish possible relationships between the ice coverage fluctuations and the main atmospheric and oceanic indices. Essentially, no statistical connection with the main atmospheric indices (Arctic and North Atlantic Oscillations) was found, but the feedback with the Atlantic Multi-decadal Oscillation index had been established. The maximum correlation coefficients for Spitsbergen are observed in the winter season, while in the area of Franz-Joseph Land this takes place in summer, which may be attributed to the final velocity of the Atlantic Multidecadal Oscillation signal.На основе спутниковых данных выполнен сравнительный анализ ледовых условий в водах, омывающих архипелаги Земля Франца-Иосифа и Шпицберген. Исследуются сезонная и многолетняя изменчивость ледовых условий, изменение ледовой обстановки, а также связь ледовых условий с основными океаническими и атмосферными индексами за 1979–2019 гг
О выделении айсбергообразующих льдотрясений по сейсмоинфразвуковым данным
Get PDFThe application of a joint method of recording seismic and infrasound signals generated during ice calving from the terminal part of the outlet glaciers to identify the process of iceberg formation is considered. For many years, the Kola Branch of the Geophysical Service of the Russian Academy of Sciences has been developing technology for remote monitoring of the processes of destruction of ice sheets in the Arctic. To improve the methodology of geophysical monitoring of processes of the iceberg calving in the Arctic seas in the Svalbard archipelago, the experiment was conducted for the first time on the complex recording of the destruction of the Nordenskiold glacier using seismometers, infrasound microphones and video cameras. The aim of the experiment was to obtain time-synchronized recordings of seismic, infrasound and video signals produced by calving of the glacier edge. The synchronized recordings obtained as a result of the experiment were used to identify specific attributes that characterize the recordings of iceberg-inducing ice quakes. Results of the experiment showed that the calving events that produce floating icebergs generate seismic and infrasonic signals of a special spectral composition and are characterized by the presence of pronounced bands in the spectral-time representation. The revealed characteristic is a distinguishing evidence of a calving event with the iceberg-inducing potential from other types of ice quakes, such as cracking and movement of the glacier body. The experimental results obtained may be used for development of a system for seismic-infrasound monitoring of processes of the iceberg formation.Рассматриваются результаты эксперимента по комплексной регистрации процессов деструкции ледника Норденшельда (архипелаг Шпицберген) при помощи сейсмометров, инфразвуковых датчиков и видеокамер. Задачи эксперимента заключаются в регистрации синхронизированных по времени сейсмических, инфразвуковых сигналов и видеозаписей, генерируемых обрушением края ледника, выявлении характерных особенностей этих сигналов, а также проверке возможности применения метода совместного сейсмического и инфразвукового мониторинга для обнаружения случаев образования айсбергов. Анализ полученных данных показал, что калвинговые события, порождающие плавающие айсберги, генерируют сейсмические сигналы особого спектрального состава, которые характеризуются наличием ярко выраженных полос в спектрально-временнóй диаграмме
Оценка термического сопротивления снежного покрова по температуре грунта
Get PDFClimate changes have influence on the thermal stability of permafrost soils. The assessment of its changes should be made taking account of the parameters of the snow cover and its thermophysical characteristics. A method for determining the thermal resistance of snow cover and the effective coefficient of thermal conductivity of snow based on ground temperature is proposed for areas of the Arctic zone of the Russian Federation with negative ground temperatures. From data on ground temperature measurements at depths of 20 and 40 cm obtained from hydrometeorological stations, it is possible to estimate the heat flow from the ground into the snow cover and, at a known air temperature and snow depth, to calculate the thermal resistance of the snow and the effective coefficient of thermal conductivity. In this case, the obtained value of the thermal conductivity coefficient of snow will include all the features of the snow cover development by the time of measurement. To develop a method for determining the thermal resistance of snow cover and the effective coefficient of thermal conductivity of snow, numerical experiments were performed using a mathematical model, which allowed establishing the conditions for the applicability of the method. The paper presents results of calculations of the thermal resistance and thermal conductivity of snow cover made by the proposed method for winters of 2006/07 and 2009/10 in Yakutia for the snow cover of different thickness composed mainly by semi-skeletal and skeletal crystals of deep frost, reaching a diameter of 3–5 mm. The use of this method for the conditions of the Yakutsk with a known type of snow formation confirmed its effectiveness.Предложена методика определения термического сопротивления снежного покрова и эффективного коэффициента теплопроводности снега по температуре грунта, температуре воздуха и толщине снежного покрова. Для отработки методики определения термического сопротивления снежного покрова и эффективного коэффициента теплопроводности снега выполнены численные эксперименты на математической модели, которые позволили установить условия применимости разработанной методики. Для условий Якутска с известным типом развития снежной толщи установлена высокая эффективность её использования
Морской лёд Арктического бассейна в свете современных и прошлых климатических изменений
Get PDFData from satellite observations (1979–2020) showed that over the last 40 years, years with a decrease in the area of summer ice extent and their thickness have prevail. Over 10 years, negative trends in anomalies of ice area and thickness of the ice are −13 and −15%, respectively. There is also a rapid reduction in the area of old ice (> 4 year-old): while in 1985 it was estimated at 2.7 million km2 while in March 2010 it was 0.34 million km2 . The paper analyses paleo-sea ice extent during the Holocene (the last 12,000 years) based on empirical biomarkers IP25 (a sea ice proxy with 25 carbon atoms synthesized by the specific Arctic sea ice diatoms Haslea spp. which have been proven to be a suitable proxy for paleo-sea ice reconstructions) obtained from deep-sea cores from the North Atlantic. The data obtained showed that during the warm periods of the Early and Middle Holocene, the area of summer sea ice was reduced to a minimum. This confirms the conclusion made earlier in [28] that the current trend of reducing the area and thickness of ice is unprecedented over the past 1,500 years. There is no complete analogue of the climate in the past corresponding to the current level of the CO2 concentration in the atmosphere. The closest time interval in terms of CO2 content is the warming of the Middle Pliocene between 3 and 4 million years ago, when the CO2 content in the atmosphere was 450–500 ppm against approximately 420 ppm at present. Paleo-climate reconstructions for this period estimate the global temperature to be 3.0–3.5±0.5 °C higher than at the end of the 19th century. Summer air temperatures in the high latitudes of the Northern Hemisphere exceeded the current ones by 8–10 °C, and the sea ice in the Arctic shelf seas was completely absent in the summer. Empirical data and model simulations have shown that presently the main driver of the reduction of the Arctic sea ice area is the increase in concentration of CO2 in the atmosphere. At the present time old sea ice tends to be replaced by seasonal ice demonstrating natural shift from predominance of permanent ice to the ice-free Arctic. In case of continuous increase in CO2 concentration in the atmosphere despite the emission control measures, one of the scenarios, which had happened in the past, may come true.За период спутниковых наблюдений (1979–2020 гг.) происходит постоянное уменьшение площади летних льдов и их толщины со скоростью 13 и 15% за 10 лет соответственно. Отмечается быстрое сокращение площади льдов старше четырёх лет и увеличение площади однолетних льдов. Анализ данных о состоянии морских льдов в Арктике за голоцен, за тёплую стадию последнего межледниковья и середину плиоцена показал, что в тёплые эпохи прошлого площадь летних льдов сокращалась до минимальных значений. Эмпирические данные и результаты моделирования показывают, что в настоящее время запущен механизм замещения многолетних льдов сезонными, что является естественным состоянием перехода от этапа преобладания сезонных льдов к безлёдной Арктики. Основной драйвер современного сокращения морских льдов – рост содержания СО2. Если концентрация СО2 в атмосфере будет увеличиваться, то может сработать один из сценариев, имевший место в прошлом