Изотопный состав ледяных кернов, полученных на Западном плато Эльбруса

The results of the isotopic investigations of several ice cores obtained at the Western Plateau of Mt. Elbrus (the Caucasus) are presented. There is a distinct seasonal cycle in the isotopic composition record in these cores. Mean annual and seasonal values of the isotopic composition and accumulation rate were reconstructed for 89 years (1924–2012). These values were compared with the available regional meteorological data and the atmospheric circulation characteristics. It was shown that in the summer season the isotopic composition reflects the local temperature while in winter it depends on the atmospheric circulation.Представлены результаты изотопных исследований нескольких ледяных кернов, полученных на Западном плато Эльбруса (Кавказ). В изотопном составе кернов прослеживается чёткий сезонный сигнал. Рассчитаны среднегодовые и среднесезонные значения изотопного состава и скорости снегонакопления за 89 лет (с 1924 по 2012 г.). Эти значения сопоставлены с данными метеонаблюдений в регионе и с характеристиками циркуляции атмосферы. Показано, что в тёплый период года изотопный состав зависит от температуры воздуха в регионе, а в холодный – от особенностей циркуляции атмосферы

Изотопные характеристики атмосферных осадков в Приэльбрусье

The aim of the work was to study the isotopic characteristics of precipitation to establish the dependence of δ18O values on temperature at the time of precipitation and to get closer to understanding the processes that form the isotopic signature of the Elbrus snow cover and glacial ice. The sampling of precipitation was organized at Azau station, located at the foot of Elbrus at an altitude of 2300 m for the period from May 01.2019 to September 27.2021. The sampling was carried out once a day at 9:00 Moscow time. The air temperature was recorded at the meteorological station in the Terskol village (Roshydromet station No. 4334250). To study the main features of long-range air transport and possible sources of moisture, 5-day back trajectories were reconstructed using the NOAA HYSPLIT_4 trajectory model. The results showed that precipitation in the Elbrus region in winter was associated with the prevailing transfer from the Atlantic, in summer – with the predominance of transfer from the regions of Central Europe, the Mediterranean and Black Seas. The Mediterranean Sea in all seasons was the area from which the air and moisture were transferred to Elbrus. The values of δ18О and δ2 Н of precipitation varied from 0.52 to −28.22‰ and from 16.3 to −224.1‰, respectively, revealing regular seasonality with high values of δ18О and δ2 Н in summer and low in winter. The deuterium excess varied over a wide range from 24.8 to −14.6‰. All obtained values of δ18О and δ2 Н were approximated by the equation δ2 Н = 8δ18О + 7.06 (R2 = 0.98), which was close to the global meteoric water line. In general, for 2 years of observations, the relationship between the δ18О values of precipitation and the temperature of the surface air layer was expressed as 0.85‰/°С. Total mean absolute error in the reconstruction of air temperatures from the δ18О value of precipitation was 3.2°С due to objective reasons and also differences in meteorological conditions of two years of observations.Приведены результаты изучения изотопных характеристик осадков, выпадающих у подножия южного склона Эльбруса, Кавказ. Отбор осадков организован на станции Азау (абс. высота 2300 м) на ежедневной основе. Установлены основные источники осадков для Приэльбрусья с применением метода обратных траекторий движения воздушных масс. Значения δ18О осадков содержат выраженную связь с температурой приземного слоя воздуха: Δδ18О/ΔT = 0.85‰/°С

Изотопный состав снега и льда на ледниках Новой Земли

In 2015–2016 during the research expeditions of Institute of Oceanology, Russian Academy of Sciences the study of stable water isotopes (18O and D) was conducted on glaciers of Novaya Zemlya. As a result, first data on isotopic composition of seasonal snow cover and glacial ice of different ages were obtained and its connection to recent climate change has been shown. The first studies of the isotopic composition of snow cover and glacial ice at Novaya Zemlya allowed determine the average values and the range of variability of δ18O and δD. It shown that for the Northern ice cap glacial ice δ18O vary within −13.91 ÷ −15.83 ‰ with an average value of −14.93 ‰ and −103,95 ÷ −116.75 ‰ for δD at −109.88 ‰ mean value. The maximum variations were recorded for summer snow samples (−8.35 ‰ for δ18O and −55.79 ‰ for δD), as well as for the horizon of superimposed ice (−20.67 ‰ for δ18O and −151.48 ‰ for δD) where isotopic composition has been inherited from winter precipitation. Insignificant differences in the coefficients of the meteoric water regression equation for precipitation on GNIP stations and glacial ice at Novaya Zemlya indicate similar conditions of air masses and precipitation formation both at GNIP station and on glaciers. Deuterium excess showed no seasonal fluctuations, and its values did not exceed 15 ‰, which shows that the proportion of continental precipitation of moisture is very low. Analysis of isotopic profiles obtained on the glaciers of Novaya Zemlya indicated the presence of significant melting. This applies not only to the modern shallow horizons, but also to the part of the glacial strata that formed in the highest part of the archipelago close to ice divide and came to the surface at the Serp i Molot Glacier tongue. Therefore, in terms of ice core palaeogeographic reconstructions the most interesting site is the highest part of the Northern ice cap where it is possible to assume the existence of colder horizons formed during the Little Ice Age and where the seasonal geochemical signal may be preserved.В 2015–2016 гг. проводились исследования стабильных изотопов 18О и D на ледниках Новой Земли. Установлены средние значения и диапазон изменчивости δ18O и δD. Показано, что для Северного ледникового купола величины δ18O в ледниковом льду варьируют в пределах −13,91 ÷ −15,83 ‰ при среднем значении −14,93 ‰. В изменениях эксцесса дейтерия не выявлено никаких сезонных колебаний, а его значения не превышают 15 ‰, что показывает крайне незначительную долю континентальной влаги в выпадающих осадках. Анализ изотопных профилей, полученных на ледниках Новой Земли, свидетельствует о значительном таянии

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

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.