41 research outputs found
SYNGAS PRODUCTION BY CO2 REFORMING OF CH4 OVER Ni-CONTAINING XEROGEL Al2O3-ZrO2(Yb2O3) WITH POLYVINYLPYRROLIDON
Изменения ледника Чалаати (Грузинский Кавказ) с малого ледникового периода по данным космогенных изотопов (10Be) и дендрохронологии
Glacier variations over the past centuries are still poorly documented on the southern slope of the Greater Caucasus. In this paper, the change of Chalaati Glacier in the Georgian Caucasus from its maximum extent during the Little Ice Age has been studied. For the first time in the history of glaciological studies of the Georgian Caucasus, 10Be in situ Cosmic Ray Exposure (CRE) dating was applied. The age of moraines was determined by tree-ring analysis. Lichenometry was also used as a supplementary tool to determine the relative ages of glacial landforms. In addition, the large-scale topographical maps (1887, 1960) were used along with the satellite imagery – Corona, Landsat 5 TM, and Sentinel 2B. Repeated photographs were used to identify the glacier extent in the late XIX and early XX centuries. 10Be CRE ages from the oldest lateral moraine of the Chalaati Glacier suggest that the onset of the Little Ice Age occurred ~0.73±0.04 kyr ago (CE ~1250–1330), while the dendrochronology and lichenometry measurements show that the Chalaati Glacier reached its secondary maximum extent again about CE ~1810. From that time through 2018 the glacier area decreased from 14.9±1.5 km2 to 9.9±0.5 km2 (33.8±7.4% or ~0.16% yr−1), while its length retreated by ~2280 m. The retreat rate was uneven: it peaked between 1940 and 1971 (~22.9 m yr−1), while the rate was slowest in 1910– 1930 (~4.0 m yr−1). The terminus elevation rose from ~1620 m to ~1980 m above sea level in ~1810–2018.Для реконструкции колебаний ледника Чалаати в Грузии использовались космические снимки, старые карты, повторные фотографии, дендрохронология, лихенометрия и анализ космогенных изотопов. Максимальное наступание ледника в начале малого ледникового периода произошло в ~1250–1330 гг., второй максимум, когда ледник достиг почти такой же длины, датируется примерно 1810 г. С этого времени до 2018 г. площадь ледника уменьшилась с 14,9±1,5 до 9,9±0,5 км2 (33,8±7,4%, или ~0,16% год−1), а его длина сократилась на ~2280 м
Пространственно-временнáя изменчивость снегонакопления на Западном плато Эльбруса (Центральный Кавказ)
Cold glaciers in the middle latitudes are considered unique archives of environmental and climate change. However, alpine ice cores are difficult to interpret, since dynamic changes can occur over very short distances. Detailed radar survey can be used to assess the effect of ice inflow from areas with different conditions of snow accumulation on the surface compared to the drilling point on the isotopic and chemical record in the glacier core. The results of radar studies on the Western plateau of Elbrus (Central Caucasus), located at an altitude of 5100–5150 m above sea level, are presented. A high-frequency ground-based radar survey was carried out in the summer of 2017 to assess the spatial and temporal changes in snow accumulation in the upper (near the top area) part of Elbrus. The ZOND 12-e GPR (ground-penetrating radar, Radar Systems, Inc.) with 500 and 300 MHz shielded antennas was used. The receiving time window was set to 100 ns (500 MHz antenna) and 470 ns (300 MHz) to obtain reflection in the depth range of about 10 m and 50 m, respectively. The results of the GPR sounding are confirmed by data on the stratigraphy, density and chemical composition of the snow-firn thickness from a shallow (24 m) borehole. The density profile made it possible to identify peaks and corresponding ice crusts of 1–2 cm thick that formed during warm periods. The internal reflections, clearly visible on the radar profiles up to 50 m deep, are of isochronous origin and have been interpreted as the boundaries of annual and seasonal layers. Detailed maps of the distribution of snow accumulation covering the cold and warm seasons of 2015–2017 have been obtained. The average thickness of seasonal snow cover on the plateau during this period was equal to 2.07 m, with minimum and maximum values of 0.2 and 3.9 m, respectively. The average values of the water storage in seasonal horizons range from 754 to 1126 mm W.E., while the annual accumulation for the 2015/16 and 2016/17 balance years amounted to 2004 and 1874 mm W.E., respectively. The data obtained were used in 2018 to determine the optimal location for deep core drilling and will further serve as the basis for modeling the age of ice on the Western Plateau of Elbrus.По данным наземного высокочастотного радиозондирования летом 2017 г. на Западном ледниковом плато Эльбруса (Центральный Кавказ) установлено, что аккумуляция снега в привершинной области характеризуется значительной изменчивостью, а также имеет сезонные различия. Анализ полей аккумуляции показал, что в средней части плато снега накапливается меньше, чем в восточной и западной, но распределение снега по площади плато аналогично из года в год. В тёплый период снегонакопление в среднем больше, чем в холодный, и происходит оно более равномерно по площади плато
Причины неопределённости в палеоклиматических реконструкциях по изотопному составу кислорода ледникового льда Эльбруса (Западное плато)
A study of the isotope signature of glacial ice in the Western Elbrus Plateau (the Caucasus) was made on the basis of five ice cores obtained in different years with high resolution. It was shown that the isotopic characteristics of ice are associated with the processes of accumulation and wind scouring of snow. Three ice cores were obtained in 2013 (C–1, C–2 and C–3), one in 2017 (C–4) and one more in 2018 (C–5). Core sampling was performed with a resolution of 5 cm. Isotopic analysis was done at the CERL laboratory (AARI) using a Picarro L2130-i isotope analyzer, the accuracy was 0.06‰ for δ18O and 0.30‰ for δ2Н. The values of d18О and δ2Н of the ice of the Western Plateau generally vary from –5 to –30‰ and from –18.7 to –225.8‰, respectively, with well-defined seasonality. Comparison of the isotope record for all cores showed that the differences in accumulation for individual seasons reach 0.3 m w. eq., differences in accumulation for individual seasons averaged over 5 years is approximately 0.2 m w.eq. The absolute differences in the average seasonal values of d associated with wind scouring and spatial redistribution of snow (deposition noise), averaged over 5 years, reached 1.38‰. The irregularity of precipitation amount within the season and errors in core dating are an additional contribution to non-climate variance (noise of definition). The absolute difference in the average seasonal values of δ18O associated with this type of noise averaged over 5 years is 1.7‰. Thus, the total uncertainty for two different types of noise can be estimated at 2.2‰, which is about 20% of the annual seasonal amplitude of δ18O values of the glacier ice in the Western Plateau (the average difference between the δ18O values of warm and cold seasons is ~10–11‰). One of the problems of linking the isotope record to the annual temperature record at the weather station was solved by using ammonium concentrations for dating the C-1 ice core and calculating the “ide+al” annual variation of δ18O values by a cosine function of the annual amplitude. Using ammonium ion (NH4) concentration each annual layer in C-1 ice core was divided into two parts associated to snow deposition in winter and in summer. It also showed δ18O values associated to change of seasons. The calculation of the cosine function showed the simplified δ18O values for each month of a particular year, due to which the δ18O values of the season boundaries in the ice core were linked to calendar months. This assimilation allowed us to compare the obtained average seasonal values of δ18O from the core with instrumental observations at the Klukhorskiy Pass meteorological station. The δ18O values of winter seasons have a weak relationship with surface temperatures, not only due to wind erosion, but also due to the high interannual variability of snow accumulation. At the same time, the average δ18O values of the warm seasons are significantly positive correlated with surface temperature (r = 0.7, p = 0.1), so ice core δ18O records can be used as a temperature proxy of the warm period.Выполнены измерения изотопного состава кислорода в неглубоких кернах, полученных в разные годы на Западном плато Эльбруса. Совмещение изотопной записи (δ18O) по глубине для трёх кернов показало, что в пределах локального участка Западного плато до 330 мм вод. экв. в слое годовой аккумуляции, т.е. около 20% средней годовой аккумуляции может быть сформировано за счёт перераспределения выпавшего снега. Неточности в реконструкции температур по среднесезонным значениям δ18O связаны с изменением сезонных пропорций в накоплении снега и с неравномерностью выпадения осадков внутри сезонов.
Изотопный состав кислорода снежно-фирновой толщи на Восточной вершине Эльбруса
The isotopic composition of oxygen of the snow-and-firn and snow thickness on the Eastern peak of Elbrus had been studied. In 2006-2008, a number of snow samples were taken in the near-peak area of Elbrus to analyze the isotopic composition of them. The drilling was performed at the crater of the Eastern peak in 2006 (64 samples) while in 2017 the samples were taken from snow pit (25 samples). Another core to a depth of 23.8 m was extracted at the Western Plateau (118 samples) for the purpose to compare local 518О values with samples from the Eastern peak. The δ18О values in the snow-and-firn thickness from the crater of the Eastern peak vary from -6.8 to -19.41 %o with the average value of -12.61 %o. It was revealed that snow layers with extremely low values of δ18О (down to -30 %) found on the eastern slope were absent on the western plateau. The loss of part of the annual isotope precipitation signal due to the winter extra light horizons could be caused by two reasons: wind drift of the freshly deposited snow, as well as the absence of part of the winter snowfalls with isotope-light precipitation at altitudes higher 5300 m. Seasonal variations of δ18О values, equal to 12 % and found in the snow-and-firn thickness on the Eastern peak, indicate that formation of the isotopic characteristics of snow is determined here by the equilibrium Rayleigh condensation and this is associated with the annual amplitude of the air temperature by a coefficient of 0.6 %o/°C. In the isotopic record obtained on the Western plateau of Elbrus, the relationship of values δ18О with the condensation temperature may be disturbed due to the frequent change of the main moisture-bearing air masses. This leads to significantly different δ18О values in precipitation at the same temperatures (the connection of seasonal δ18О values with the annual amplitude of air temperature varies from 0.3 to 1.12 %о/°С).Установлены сезонные вариации значений δ18О в снежно-фирновой толще на Восточной вершине Эльбруса от -6,8 до -19,41 %о при среднем значении -12,61 %о. В отличие от Западного плато здесь отсутствуют слои снега с экстремально низкими значениями δ18О. Потеря части годового изотопного сигнала осадков за счёт зимних экстра лёгких горизонтов связана с ветровым сносом уже отложенного снега и отсутствием части зимних снегопадов с изотопно лёгкими осадками на высотах более 5300 м
Гляциоклиматические исследования Института географии РАН в кратере Восточной вершины Эльбруса в 2020 г.
During the field campaign in August 18–30, 2020 the meteorological regime and heat balance of the glacier surface were investigated in the crater of Mt Elbrus Eastern Summit (5600 m a.s.l.) together with the GPR measurements of the ice thickness and seasonal snow cover. Preliminary data analysis allowed the following features: the predominance of synoptic fluctuations over the diurnal ones; the high values of average and maximum wind speed associated with the impact of jet streams and with influence of leeward storms; extremely high temporal variability of relative humidity and its very high deficit in cloudless conditions conducive to intensive evaporation and sublimation from the snow surface. The maximum thickness of ice in the crater reaches 100 m, and the average is 34 m. A new ice core with a length of 96.01 m from the glacier surface to its bed had been obtained. The drilling speed varied from 11 to 1 m/h, decreasing with depth from 4.5 to 4.0 m/h on average. The thickness of the snow-firn mass is about 20 m, which is three times less than on the Western Plateau of Mt Elbrus. According to measurements in the borehole, temperature at the glacier bed is −0.6 °C. The calculated heat flux is 0.39 W/m2. Air sampling was carried out in the crater of the Eastern Summit of Elbrus and on the Garabashi glacier. Repeated measurements of the soil temperature in the fumarole field on the outer edge of the crater of the Elbrus Eastern Summit allow the conclusion that the temperature regime is stable.С 18 по 30 августа 2020 г. в кратере Восточной вершины Эльбруса впервые проводились наблюдения за метеорологическим режимом и тепловым балансом ледника. Выполнена также радиолокационная съёмка толщины льда и сезонного снежного покрова, пробурена скважина от поверхности до ложа с получением керна льда, измерены температуры в скважине, в шурфе из сезонной снежной толщи отобраны образцы для изотопного, химического и спорово-пыльцевого анализа, на поверхности фумарольного поля и в атмосфере над ледником взяты образцы газа, продолжен мониторинг температуры грунта на фумарольной площадке
Пути дальнего переноса пыли на ледники Кавказа и химический состав снега на Западном плато Эльбруса
We present and discuss the chronology of dust deposition events documented by the shallow firn and ice cores extracted on the Western Plateau, Mt. Elbrus (5150 m a.s.l.) in 2009, 2012 and 2013. Snow and ice samples were analysed for major ions and minor element concentrations including heavy metals. Dust layers are formed on the surface of the glaciers as a result of atmospheric transport of mineral dust and aerosol particles to the Caucasus region. Satellite imagery (SEVIRI), trajectory models, and meteorological data were used for accurate dating of each the dust layers revealed in the ice cores. Then we tried to determine origins of the dust clouds and to investigate their transport pathways with high resolution (50–100 km). It was found that the desert dust is deposited on Caucasus glaciers 3–7 times in a year and it comes mainly from deserts of the Middle East and more rarely from the Northern Sahara desert. For the first time average annual dust flux (264 µg/cm2 per a year) and average mass concentration (1.7 mg/kg) over the period 2007–2013 were calculated for this region. The deposition of dust resulted in elevated concentrations consists of mostly ions, especially Ca2+, Mg2+, K+, and sulphates. Dust originated from various sources in the Middle East, including Mesopotamia, or similar dust clouds passing over the Middle East are characterised by high concentrations of nitrates and ammonia that may be related to atmospheric transport of ammonium from agricultural lands that may explain high concentrations of ammonium in the dust originating from this region. Mean values of crustal enrichment factors (EF) for the measured minor elements including heavy metals were calculated. We believe that high content of Cu, Zn and Cd can be a result of possible contribution from anthropogenic sources. Studies of the Caucasus ice cores may allow obtaining new independent data on the atmosphere circulation and high-altitude environment of this region.Исследованы образцы из снежных шурфов и керна из неглубоких скважин, пробуренных на Западном плато Эльбруса на высоте 5100 м в 2009, 2012 и 2013 гг. Образцы снега и льда проанализированы на содержание основных соединений и микроэлементов, включая тяжёлые металлы. В результате переноса минеральных частиц на ледники Кавказа в снежно-фирновой толще формируются отчётливо различимые горизонты загрязнения. Анализ космических снимков SEVIRI, полей оптической толщины атмосферы, траекторий движения воздушных масс и метеорологических данных позволил определить первичные источники минеральных частиц для переноса пыли с высокой точностью (50–100 км). Cоставлена хронология событий переноса пыли. Установлено, что такие явления происходят на Кавказе 3–7 раз в год. Пыль принесена на ледники Эльбруса с Ближнего Востока и из Северной Африки. Выполнено первое для Кавказа прямое определение количества твёрдого вещества, выпадающего из атмосферы на поверхность на больших высотах – 264 мкг/см2 в год. Химический анализ образцов снега из горизонтов загрязнения, образовавшихся в 2009 г., показал высокое содержание нитратов, аммония и сульфатов, что связано с поступлением пыли из сельскохозяйственных районов в Месопотамии. Обнаружено повышенное содержание Cu, Zn и Cd по сравнению с естественным фоном, что может указывать на повышенный региональный фон этих элементов в Северной Африке и на Ближнем Востоке, а также на вероятный вклад антропогенных аэрозолей.