Ice and Snow (E-Journal) / Лёд и Снег
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Возраст морен ледника Большой Азау в верховьях долины реки Баксан по дендрохронологическим данным
Get PDFBasing on treering analysis of more than 150pines growing in the Azau clearing, the minimum age of the deposits created by the Greater Azau Glacier was identified. Historical evidence, cartographic data, remote sensing materials, as well as the results of lichenometric studies and radiocarbon dating of buried soils were used as additional sources of information. We determined limits of the area covered by the glacier tongue at the end of the 19th century. It was also shown that the highest and most pronounced lateral moraine, conventionally called the «17th century moraine», was formed earlier than the end of the 15th century. Judging from the size of the maximum lichens of Rhizocarpon geographicum (120–130mm) on its surface, the age of the moraine, determined by the dendrochronological method was found to be underestimated. It may be several centuries older than the end of the 16th century. We reexamined a pine trunk buried in the sediments at the bottom of the valley which was discovered in the 1960s. Previously it was dated by radiocarbon (140±75BP[1], the calibrated date– 1650–1960 CE). According to the new data, the most probable treering dates of the buried tree are 1759–1883CE, however, the second most likely dates are 1826–1950CE. Unfortunately, low statistical estimates do not allow us to confirm the reliability of the dates. The paper also discusses the controversial issue of the position of the moraine of 1849CE, which was described by H.Abich[2]. The annex to the article contains a translation of a fragment of this important paper related to the Greater Azau Glacier. Suppressions of pine growth from the moraines of the Greater Azau in the 1640s, 1710s, 1800s, 1840s, and 1860sCE are synchronous with the advances of the Bosson, Mer de Glace and Grindelwald glaciers in the Alps[3].На основе анализа дендрохронологических данных, радиоуглеродных датировок и исторических свидетельств рассмотрена история колебаний ледника Большой Азау в малый ледниковый период. Дискутируется вопрос о положении морены максимума наступания ледника в 1849г., описанного Г.Абихом. Определён минимальный возраст морен, в том числе береговой, которую ранее относили к XVII в
Сохранность климатического сигнала в слоях древнего льда в районе Купола В (Антарктида)
Get PDFIn this work we have presented the results of numerical modeling of the age and temperature distribution in ice layers at Dome B site (79,02° S, 93,69° E, altitude 3807 m a.s.l., ice thickness about 2.5 km), located 300 km to the west from Russian Antarctic station Vostok. Dome B is situated on the onset of the ice flow line passing through deep borehole 5G, and is considered as one of the most promising places to search for and to study the Easth’s oldest ice with the age of up to 1.5 Ma. According to our calculations, all realistic scenarios show the ice age at 60 m above the ice base to be considerably older than 1 Ma, and the glacier base temperature is well below the pressure melting point (−1.8 °С for pressure = 23 MPa). For the most likely scenario (accumulation rate 1.8 g/(cm2 year), effective ice surface temperature −64 °С and geothermal heat flux 60 mW/m2) the ice age is 1.4 Ma and the basal temperature is about −13 °С that is close to the earlier predictions from a 2D‑model. Maximum estimate of the «diffusion length» in the old ice (for the scenario in which the basal temperature reaches the melting point, and in which 30% of «excess diffusion» is taken into account) is 5.2 cm. In 1.4 Ma-old ice a 40-ka climatic cycle is squeezed into a 290-cm thick ice layer. For this ratio of wave length and diffusion length the climatic signal attenuation (ratio between the signal amplitude after and before the diffusive smoothing) is 0.6%. Thus, due to the relatively low ice temperature here we may expect a nearly undisturbed climatic curve in the old ice core that will be drilled one day at Dome B. At the same time shorter oscillations with the wavelengths of < 1500 years will be totally erased by diffusion.Представлены результаты моделирования возраста и температуры льда для Купола В (79,02° ю.ш., 93,69° в.д., высота 3807 м над ур. моря, толщина льда около 2,5 км) в Антарктиде. Для всех сценариев возраст льда на отметке 60 м выше ложа ледника составляет более 1 млн лет, а для наиболее вероятного сценария – 1,4 млн лет. Температура ложа для всего диапазона реалистичных оценок геотермального потока тепла находится ниже точки плавления и для наиболее вероятного сценария равна около −13 °С. Расчётное ослабление амплитуды 40‑тысячелетнего климатического цикла в древнем льду за счёт молекулярной диффузии составляет около 0,6%. Результаты исследования позволяют сделать вывод, что Купол В – перспективное место для извлечения нового глубокого керна, с помощью которого можно будет получить ненарушенный климатический сигнал за последние 1,4 млн лет
Информативность гидрометеорологических и астрогеофизических факторов в задаче описания межгодовых колебаний ледовитости Гренландского моря
Get PDFThe interannual changes in ice coverage in the Greenland Sea for the winter (December–April), spring (May– June), summer (July–September), and autumn (October–November) seasons for the period 1950-2018 are considered. The presence of negative linear trends and the polycyclic oscillations of the ice coverage variability for all seasons has been confirmed. Using spectral analysis, the dominant fluctuations from 5 to 22 years were identified. The cross-correlation method allowed us to determine the significant relationship of the Greenland Sea ice coverage with hydrometeorological and astrogeophysical factors. The statistically significant relationship of the ice coverage for a concrete year with similar characteristics for a previous period persisting up to three years had been noted. The highest cross-correlation coefficients were noted in the winter and spring seasons. The ice coverage of the autumn season demonstrates the persistence of the inertia of ice conditions for up to two years. The analysis of correlations with astrogeophysical parameters revealed the closest relationship between the ice coverage and the longitude coordinate of the Earth's pole position, the nutation parameters of the Earth's axis, and the distance between the Earth and the Sun. When constructing the multi-regression equations, we investigated the informativeness of various hydrometeorological and astrogeophysical factors in the models of the ice coverage variability for each season. The following estimates of quality of the models were obtained: correlation coefficients (up to 0.89), determination coefficients (to up 0.80), and a model reliability which depends on the admissible forecast error and includes the mean square deviation of the investigated value) – up to 99%). The informativeness of various factors was estimated and the contribution to the total variance was revealed: hydrometeorological factors – up to 70%; astrogeophysical factors – up to 50%. The obtained statistical equations can be used for the diagnosis and for development of methods for the very-long-term forecast of the Greenland Sea ice coverage.Подтверждены отрицательные линейные тренды и полицикличность ледовитости Гренландского моря. Установлена тесная связь изменения ледовитости с температурой воздуха и индексами атмосферной циркуляции, а также с долготной координатой положения полюса Земли, параметрами нутации оси Земли и расстоянием между Землей и Солнцем. Получены физико-статистические уравнения изменения ледовитости для всех сезонов с учётом влияния различных факторов и оценена их информативность по вкладу каждого фактора в общую дисперсию. На долю гидрометеорологических индексов приходится до 70%, астрогеофизических – до 50%
Расчёт экстремальных толщин и прочностных характеристик однолетнего ледяного покрова Карского моря с помощью термодинамической модели
Get PDFUsing the example of the Kara Sea, the possibility to calculate values of the thickness and strength characteristics of ice of rare occurrence for areas of marine waters with seasonal ice cover, where field observations are absent, is considered. A method for obtaining climatic characteristics of meteorological elements for conditions of different occurrence (extreme values) has been developed. It is based on the selection of a statistical distribution law for the «freezing degree-days» (FDD). On the basis of the obtained sums of the degree-days, the restoration of daily values of the air temperature is carried out. This technique can be applied to areas of the Arctic seas with seasonal ice cover. The obtained climatic characteristics allow us to estimate the strength properties and thickness of sea ice using a thermodynamic model. The proposed method makes it possible to calculate values of the thickness and strength characteristics of ice for the entire water area of the Kara Sea. For average climatic conditions, the calculated estimates of the periods of stable ice formation, thickness and strength characteristics of ice are in good agreement with the results of field observations. It is established that the moment of maximum ice strength does not coincide with the time when the ice reaches its maximum thickness. The characteristics of the ice cover calculated for conditions of rare occurrence also do not contradict the values observed in nature. The differences in the duration of the ice season in the south-western part of the sea from the north-eastern part, obtained under climatic conditions of different occurrence, are shown.Для оценки прочностных свойств и толщины морского льда использована методика получения климатических данных при условии разной повторяемости, которая может применяться для арктических морей с сезонным ледяным покровом. Проведены расчёты толщины и прочностных характеристик льда Карского моря для разных климатических условий. Полученные расчётные значения сроков устойчивого ледообразования, а также толщины и прочностных характеристик льда хорошо совпадают с результатами натурных наблюдений
Строение снежной толщи на Кольском полуострове
Get PDFIn 2016–2019, the structure of the snow thickness in the northern and central parts of the Kola Peninsula (from the Barents Sea to the Khibiny Mountains) was studied in tundra, forest-tundra, taiga, high–altitude Arctic and other landscapes during the periods of maximum recrystallization of the snow (February–April) and initial snow accumulation (October). 37 borings were made in the snow thicknesses. 399 snow layers of different ages and genesis were examined. In the total, 399 measurements of the density, porosity, structure of snow (size and shape of ice crystals) and texture (orientation of crystals and pores) of snow layers, 413 measurements of temperature at the contacts between snow layers, 46 measurements of the temporary resistance of the layer to rupture, 27 measurements of the time resistance to compression, 119 measurements of the resistance of the snow layer to horizontal sounding (with a cross-shaped tip that allows taking into account the anisotropy of the snow layer) were performed. The percentage of crystals of different classes of shapes in the layer was determined. It was found that the Kola Peninsula has a high rate of evolution of the snow thickness. Even in multi-snow winters (including the landscapes of high-altitude Arctic deserts in Khibiny and Monche-tundra) in March, up to 90% of the snow thickness is made up of snow layers with a columnar and fibrous texture, composed of ice crystals of semi-skeletal and skeletal classes of shapes with a diameters of up to 4 mm. These patterns of the evolution are typical for the Arctic and Subarctic (confirmed by studies on the Yamal Peninsula, in the lower reaches of the Northern Dvina River and in Karelia). Values of the strength characteristics of the snow layer (time resistance to rupture, resistance to compression, and to horizontal sounding with regard for the anisotropy of the snow layer texture) are the lower, the higher the content of crystals in the layer of the highest stages of evolution (skeletal) and the more developed the texture of the layer. The lowest values of strength characteristics were observed in snow layers with a fibrous texture.В 2016–2019 гг. исследовалась структура, текстура и физические свойства снежной толщи в северной и центральной частях Кольского полуострова в тундровых, лесотундровых, таёжных, высокогорных арктических и других ландшафтах в периоды начального снегонакопления (октябрь) и максимальной перекристаллизации снежной толщи (февраль–апрель). В 37 шурфах было исследовано 399 снежных слоёв разного возраста. Установлено, что к марту до 90% снежной толщи состоит из снежных слоёв со столбчатой и волокнистой текстурой, сложенных ледяными кристаллами полускелетного и скелетного классов диаметром до 4 мм
Оценка пределов прочности льда на одноосное сжатие в Охотском море по данным измерений и расчётов
Get PDFThe data on the strength of sea ice obtained in the course of explorations in the Sea of Okhotsk are compared with the results of calculations for the purpose to test the applicability of analytical methods to the conditions of this Sea. Two groups of samples were used to determine the ice strength limit. The first group included samples obtained from smooth drifting ice fields, and the second one were samples obtained from ice blocks similar to hummocks on a surface of an ice field. The measured characteristics of the temperature and electrical conductivity of ice were used in calculations using empirical formulas. The calculated values of the ice strength limits were compared with the measurements. Note, that application of the ISO 19906:2008 methodology (International Technical Standard) provided greater variety of strength values of both smooth and hummocky ice, and the SP 38.13330.2012 methodology (Russian Technical Standard) underestimated the values. The algorithms from the «Guidelines for Calculating Ice Strength Limits» are suitable for estimating mean values, but do not provide comparable root-mean-square deviation values with real data of direct measurements. The results of calculating the strength characteristics allow us to conclude that to obtain the extremely possible strength values the direct measurements (field tests) are necessary. ISO 19906:2008 is most suitable for estimating the values of smooth ice from the methods under consideration, and the algorithm from the «Methodical Letter on calculating Ice Strength Limits» is better to use for an average assessment of ice blocks.Впервые для дрейфующего льда Охотского моря проведено сравнение измеренных и рассчитанных по инженерным методикам значений прочности морского льда на одноосное сжатие. Проанализирована точность российских и зарубежных алгоритмов расчёта с учётом региональной особенности ледовых условий. Сделан вывод, что средние значения прочности льда удовлетворительно воспроизводятся при помощи алгоритма В.В. Богородского, в то время как максимальные значения прочности более точно рассчитываются по методике ISO 19906:2008
Ледовый режим рек бассейна Дебед, Армения
Get PDFFor the first time, the ice regime and its changes in 1939–2018 was analyzed for one of the largest river basins in Armenia – the Debed River. The main material for the analysis was data from observations at six weather stations and 15 river posts of the Hydrometeorological Service of Armenia, which are located at different altitude levels – from the upper reaches of the tributaries at 1600–1900 m down to 450 m at the lower section. Ice phenomena on the rivers of the basin are diverse. More often these are shore ices, shuga (frazils), freeze-up, less often – ice dams and ice-drift, but everywhere they are poorly developed. The reason is the positive average monthly water temperature in winter in almost all the rivers of the basin. In most catchments, all ice formations exist for a short period – usually no longer than 50–100 days; a freeze-up is not formed everywhere and not every year, although on some of the highest tributaries it can last up to 40 days. An analysis of the long-term course of air temperature in the basin showed that against the background of its significant interannual fluctuations, a clear change took place in the early – mid-1990s. Over the 30year period from the early 1960s, temperature trends in all seasons of the year had only a small positive trend, but after the mid-1990s and until 2018, the temperature rise was accelerated significantly and steadily.The ice regime of the rivers at the beginning of the XXI century was affected not only by the warming of winters by almost 0.7 °C. A significant rise of the spring temperatures by 1.4 °C noriceably displaced the dates of the end of the ice phenomena and decreased duration of them. During the 80-year observation period, the beginning of the ice regime in the middle course of the basin rivers (at altitudes of 1000–2000 m) shifted to a later date by 10–15 days, and its end is observed 15–20 days earlier, the total duration of the ice regime decreased by 25–35 days.На основе многолетних ежегодных наблюдений (1939–2018 гг.) на 15 гидропостах и шести гидрометеостанциях в крупном горном бассейне р. Дебед (Армения) рассматриваются особенности ледового режима рек на разных высотах. На всём водосборе ледовые явления развиты слабо, что объясняется положительной среднемесячной температурой воды в реках в зимний период. Показано, что влияние общего потепления климата в течение периода наблюдений, которое значительно ускорилось на данной территории с начала 1990-х годов, и особенно повышение зимних и весенних температур воздуха в начале ХХI в. привели к смещению всех сроков ледовых явлений на реках и сокращению средней их продолжительности на 30 дней
Метеорологический режим Сыгыктинского ледника (хребет Кодар) в период абляции
Get PDFMeteorological parameters measured over two months by two automatic weather stations on the Sygyktinsky glacier and its terminal moraine (Kodar ridge, South of Eastern Siberia, 56.9° N, 117.4° E) were used to study the physical processes controlling the summer ablation of the glacier. The meteorological regime of the glacial zone is conditioned by large-scale atmospheric circulation and characterized by steadily positive air temperatures (7.2±4.5 °C), high relative humidity (76±23%), significant cloud cover (66%), a predominance of low-intensity precipitation, and low wind speeds (1.0±0.8 m/s). It is found that the daily air temperatures on the glacier strongly correlate (r = 0.97) with those in the free atmosphere, so the ERA-Interim reanalysis data (at the level of 750 hPa) can be used to make longer the temperature series on the Kodar glaciers. We found significant statistical relationships between the daily ablation (29 mm day–1 on average) and relative humidity as well as with incoming shortwave radiation and cloud cover. The short-wave radiation balance (91 W/m2) is the main source of energy for melting, which depends on the albedo (average value 0.41). On days with summer snowfalls, the increase in albedo reduces the short-wave balance by 2.5 times. Explicit and latent heat fluxes are the secondary sources of melting energy, while heat loss takes place mainly due to effective long-wave radiation (–15 W/m2). The absorbed short-wave radiation on the glacier was smaller than that on the moraine, but the radiation balance was comparable on both sites owing to smaller effective LW radiation on the glacier. The dominance of the radiation factor demonstrates the important role of the solar radiation regime (cloud cover and atmospheric transparency) in the surface ablation of the Kodar glaciers.С помощью системы автоматического мониторинга с высоким временным разрешением измерены метеорологические характеристики и радиационный баланс Сыгыктинского ледника в период абляции. Исследованы колебания метеорологических параметров в ледниковой зоне и проведён их спектральный анализ. Установлено влияние радиационных и синоптических факторов на метеорологический режим ледника. Статистически определена связь метеорологических показателей со скоростью таяния, оценён вклад радиационного баланса в таяние ледника
Изотопный состав (δ18O, δ2H) снежного покрова Карелии
Get PDFFor the first time, a regional study of the isotopic composition (δ18O and δ2 H) of the snow cover in Karelia was performed using a sub-meridional and two sub-latitudinal profiles (March 2016). Snow nutrition does generally prevail here in the river and underground runoff. Integral snow samples were taken at 45 sites, three horizons were studied at 39 of them. Monitoring of the isotopic composition of atmospheric precipitation is carried out in the Petrozavodsk city from 2012 to the present. The isotopic composition of snow on the territory of Karelia varied through the following range: for δ18O it is from −15.7 to −21.1 ‰, and for δ2 H – from −118 to −158 ‰, which is significantly less than the isotopic composition of atmospheric precipitation for the same period: δ18O = −8.7 ÷ −30.9 ‰, δ2 H = −77 ÷ −239 ‰. The exception is snow in the valleys of the large Shuya and Suna rivers with light isotopes δ18O (down to −21 ‰). According to two sublatitudinal profiles in southern and central Karelia, there were no obvious trends in the isotopic composition of snow. The decrease in the contents of deuterium (δ2 H) and oxygen-18 (δ18O) in the sections of snow cover corresponds to an almost complete loss of snow at the beginning of winter due to the December thaws of 2015 and its intensive accumulation in abnormally cold January 2016. According to trajectory analysis data, air masses containing isotopically heavy moisture come mainly from the west and southwest, and those containing isotopically light moisture come from the north and east. The results of this research demonstrate that the reconstruction of the isotopic composition of winter precipitation can be approximately performed by the isotopic composition of snow cover.Приводятся результаты изотопного анализа состава снежного покрова Карелии, сформировавшегося в зимний период в 2015/16 г., и атмосферных осадков в Петрозаводске. Показано, что состав снега изменяется от −15,7 до −21,1 ‰ для δ18О и от −118 до −158 ‰ для δ2Н, а облегчение изотопного состава происходит с юга на север в соответствии с понижением температуры воздуха. Реконструкцию изотопного состава зимних атмосферных осадков приближённо можно выполнить по изотопному составу снежного покрова
