Реконструкция средних температур января в раннем голоцене на северо-востоке Большеземельской тундры

The aim of the study was to establish the period of accumulation of peatland with ice wedges near Vorkuta town based on series of calibrated radiocarbon dates, to anchor in time the isotope-oxygen curve of syngenetic ice wedge from peatland and to reconstruct the mean January air temperature for the appropriate Holocene period. Analysis of a series of 14C dates showed that peatland near Vorkuta was actively formed between 10.5 and 6 cal. ka BP. Winter conditions in the Vorkuta area were quite severe, that favored to frost cracking of the peatland and syngenetic growth of ice wedges within the drier sites and peat-soil wedges within the watered sites. Ice wedge growth was the most active within the Greenlandian Stage of Holocene, between 10,5 and 9,7 cal. ka BP, the reconstructed mean January air temperature for this period varied between −23 and −25 oC; currently, such temperatures are recorded only during the coldest winters.Вблизи г. Воркута процессы заболачивания и образования торфа начались в первой половине гренландского периода голоцена – около 11–10 тыс. калиб. лет назад. Завершилось формирование торфяника 3–2 тыс. калиб. лет назад. Время активного формирования в торфянике сингенетических повторно-жильных льдов приходится на период между 10,5 и 9,7 тыс. калиб. лет назад, когда среднеянварская температура воздуха варьировала между −23 и −25 oC

ВАРИАЦИИ ИЗОТОПОВ КИСЛОРОДА И ВОДОРОДА В СОВРЕМЕННОЙ ПЛАСТОВОЙ ЛЕДЯНОЙ ЗАЛЕЖИ В УСТЬЕ Р. АККАНИ, ВОСТОЧНАЯ ЧУКОТКА

The object of this study is a recently (or in the Holocene) formed thick (up 2.7 m in height) buried massive ice body, exposed in 2 km South-East from the mouth of the river Akkani in the North-East of Chukotka in the vicinity of the settlement Lavrentiya. The structural-textural characteristics of ice and enclosing deposits are considered. It is shown that the overlying layers of sediments are loams with a slab structure and vertical-layer medium and thin-chill cryogenic structure and ice sockets. The ice of the body is very pure and transparent, visible to a depth of 0.5 m. There are some inclusions found in massive ice: sand and loams presented in forms of thin interlayers of particles or granules. The ice is full of bubbles. The main method of the research was the analysis of isotopes of oxygen and hydrogen within the stratified ice body, and also relationships between them as well as ratios between the deuterium excess and δ2Н. The thick and relatively contemporary massive ice layer buried under a layer of proluvial sediments had been found for the first time, and together with this, the isotope variations of the buried ice (δ2Н and δ18O) were determined. The mean values of δ18О and δ2H in the ice are rather stable and equal to −17.1 and −128.3‰, respectively. These isotope characteristics may be used for cryogenic reconstructions of massive ice formations widely distributed in the late Quaternary deposits in Eastern Chukotka.Изучен изотопный состав кислорода и водорода мощного современного (голоценового) ледяного пласта, погребённого под слоем пролювиальных отложений на побережье Чукотки вблизи посёлка Лаврентия. Значения δ18О и δ2H во льду довольно однородны и составляют −17,1 и −128,3 ‰ соответственно. Изученный пластовый лёд в устье р. Аккани представляет собой захороненный перелетовывающий снежник, сформировавшийся с участием поверхностных вод и атмосферной влаги весенне-летнего периода

Реконструкция зимней температуры воздуха раннего и среднего голоцена по изотопному составу ледяных жил восточного побережья полуострова Дауркина, Чукотка

The object of research is the Holocene massive ice veins on the Eastern coast of the Daurkin Peninsula, the easternmost part of the Chukotka. Peat bogs with ice veins occur on the surface of marine terraces (near Uelen and Lorino settlements) and on flood plain of the Koolen’ Lake; the thickness of peat varies from 0.7 to 2.5 m. Radiocarbon dating of the peat enclosing the investigated ice veins near Uelen and Lorino indicated that the beginning of peat accumulation began at the end of Late Pleistocene – early Holocene, about 11 cal ka BP. On the flood plain of the Koolen’ Lake peat bogs began to accumulate in the middle Holocene, i.e. around 6 cal ka BP. At the initial stage of peat bogs formation the rate of peat accumulation was high and could reach 1 cm/10 years. Ice veins occur at a depth of 0.5–1 m, and their lower parts are located in the underlying peat sandy loams and loams. In the upper levels of the peat bogs, narrow present-day ice veins are found, which are sometimes embedded in the upper parts of Holocene veins. A clear sign of syngenetic growth of veins is the upward bending of the layers of the host peat at the lateral contacts with the veins. The main source of water for the formation of ice veins is snow, as evidenced by the ratio of stable isotopes of oxygen and hydrogen and the values of deuterium excesses in the ice. A slight admixture of saline water (probably from a seasonally thawed layer) was noted in the veins near the Lorino settlement. Reconstructions of winter air paleotemperatures, performed on the basis of data of isotope-oxygen composition of ice from the veins, did show that at the period between 11 and 6 cal Ka BP, the mean winter air temperature on the Daurkin Peninsula was by 2–5 oC lower than today, but the air temperature of the coldest month (January or February) was still lower (by 4-8 oC) than today. The noticeable trend of increase of stable isotope values in the ice veins from early Holocene to the present time is indicative of a steady positive trend of mean winter air temperatures in the Holocene.Реконструкции зимних палеотемператур воздуха на основе данных изотопно-кислородного состава льда жил показали, что между 11 и 6  тыс.  кал.  лет назад среднезимняя температура воздуха была на 2–5оС ниже современной, а температура воздуха самого холодного месяца (января или февраля) – на 4–8оС ниже современной. Установлен устойчивый положительный тренд зимних температур воздуха от раннего голоцена до настоящего времени

Два подхода к расчёту расчленения гидрографа стока реки с ледниковым питанием с помощью изотопных методов

Application of the stable isotope method in the balance equations used to calculate separation of the runoff hydrograph from the Djankuat Glacier basin is demonstrated. Simultaneous solution of equations of water, isotope and ion balances is applied to estimate contributions of different components and processes to formation of the Djankuat River runoff regime. For June 2014, we made calculations for the purpose to separate contributions of the spring (isotopically weighted) snow and winter (isotopically depleted) snow. Field works in the glacial basin Djankuat were performed during two ablation seasons, i.e. from June to September of 2013 and 2014. Two approaches were used when calculating separation of the runoff hydrograph by means of solution of systems of equations for isotopic and ion balances: 1) taking account of the isotope fractionation during snow melting, and 2) with no account for the fractionation. Separation of the hydrograph for June 2014 have shown that about 15–20% of the Djankuat River runoff is formed by spring snow melting, sometimes increasing up to 36%. Contribution of spring meltwater to the total runoff increases when the isotope fractionation during the snow melting is taken into account for the calculations. In this case, the contribution of spring snow changes from 30 to 50%.Рассмотрено применение метода стабильных изотопов в балансовых расчётах расчленения гидрографа стока с ледника Джанкуат. Изученные изотопные вариации стока на замыкающем створе р. Джанкуат для двух сезонов абляции 2013 и 2014 г. совместно с измерениями δ18О и минерализации различных источников питания р. Джанкуат (атмосферные осадки, снег разных сезонов, фирн, лёд и грунтовые воды) позволили расчленить гидрограф стока 2014 г. Применялись два методических подхода к расчётам: разделение гидрографа стока решением систем уравнений ионного и изотопного баланса с учётом изотопного фракционирования при таянии снега и без учёта фракционирования. Установлена величина погрешности расчётов с использованием значений δ18О и абсолютных концентраций 18О

Reconstruction of average January temperatures during the early Holocene in the North-East of the Bolshezemelskaya tundra

The aim of the study was to establish the period of accumulation of peatland with ice wedges near Vorkuta town based on series of calibrated radiocarbon dates, to anchor in time the isotope-oxygen curve of syngenetic ice wedge from peatland and to reconstruct the mean January air temperature for the appropriate Holocene period. Analysis of a series of 14C dates showed that peatland near Vorkuta was actively formed between 10.5 and 6 cal. ka BP. Winter conditions in the Vorkuta area were quite severe, that favored to frost cracking of the peatland and syngenetic growth of ice wedges within the drier sites and peat-soil wedges within the watered sites. Ice wedge growth was the most active within the Greenlandian Stage of Holocene, between 10,5 and 9,7 cal. ka BP, the reconstructed mean January air temperature for this period varied between −23 and −25 oC; currently, such temperatures are recorded only during the coldest winters

OXYGEN AND HYDROGEN ISOTOPE VARIATIONS IN A RECENTLY FORMED MASSIVE ICE AT THE MOUTH OF THE AKKANI RIVER, EASTERN CHUKOTKA

The object of this study is a recently (or in the Holocene) formed thick (up 2.7 m in height) buried massive ice body, exposed in 2 km South-East from the mouth of the river Akkani in the North-East of Chukotka in the vicinity of the settlement Lavrentiya. The structural-textural characteristics of ice and enclosing deposits are considered. It is shown that the overlying layers of sediments are loams with a slab structure and vertical-layer medium and thin-chill cryogenic structure and ice sockets. The ice of the body is very pure and transparent, visible to a depth of 0.5 m. There are some inclusions found in massive ice: sand and loams presented in forms of thin interlayers of particles or granules. The ice is full of bubbles. The main method of the research was the analysis of isotopes of oxygen and hydrogen within the stratified ice body, and also relationships between them as well as ratios between the deuterium excess and δ2Н. The thick and relatively contemporary massive ice layer buried under a layer of proluvial sediments had been found for the first time, and together with this, the isotope variations of the buried ice (δ2Н and δ18O) were determined. The mean values of δ18О and δ2H in the ice are rather stable and equal to −17.1 and −128.3‰, respectively. These isotope characteristics may be used for cryogenic reconstructions of massive ice formations widely distributed in the late Quaternary deposits in Eastern Chukotka

Minimal, average, and maximum values of δ¹⁸O in ice wedge of the sections from Mamontova Gora and Syrdakh Lake, Central Yakutia

The oxygen isotope composition of the Late Pleistocene and Holocene syngenetic ice wedges, exposed at Mamontova Gora and Syrdakh Lake, is determined. In the area of Mamontova Gora, δ¹⁸O is in the range of –24.7 to –30.9‰ for the Late Pleistocene ice wedges, and of –23.2 to –25.9‰ for the Holocene ice wedges. In the area of Syrdakh Lake, δ18O ranges from –29.2 to –32.5‰. Obtained isotope data allowed to reconstruct the average winter air temperatures

Radiocarbon dating of Late Pleistocene and Holocene ice wedges in Mamontova Gora, Central Yakutia

Radiocarbon dating of the Late Pleistocene and Holocene syngenetic ice wedges, exposed at Mamontova Gora, are determined. The age of the ice wedges is shown to be younger than 20 ka, but older than 10 ka BP

Winter air temperature in the early and middle Holocene on the eastern coast of Daurkin Peninsula, Chukotka, reconstructed from stable isotopes of ice wedges

The object of research is the Holocene massive ice veins on the Eastern coast of the Daurkin Peninsula, the easternmost part of the Chukotka. Peat bogs with ice veins occur on the surface of marine terraces (near Uelen and Lorino settlements) and on flood plain of the Koolen’ Lake; the thickness of peat varies from 0.7 to 2.5 m. Radiocarbon dating of the peat enclosing the investigated ice veins near Uelen and Lorino indicated that the beginning of peat accumulation began at the end of Late Pleistocene – early Holocene, about 11 cal ka BP. On the flood plain of the Koolen’ Lake peat bogs began to accumulate in the middle Holocene, i.e. around 6 cal ka BP. At the initial stage of peat bogs formation the rate of peat accumulation was high and could reach 1 cm/10 years. Ice veins occur at a depth of 0.5–1 m, and their lower parts are located in the underlying peat sandy loams and loams. In the upper levels of the peat bogs, narrow present-day ice veins are found, which are sometimes embedded in the upper parts of Holocene veins. A clear sign of syngenetic growth of veins is the upward bending of the layers of the host peat at the lateral contacts with the veins. The main source of water for the formation of ice veins is snow, as evidenced by the ratio of stable isotopes of oxygen and hydrogen and the values of deuterium excesses in the ice. A slight admixture of saline water (probably from a seasonally thawed layer) was noted in the veins near the Lorino settlement. Reconstructions of winter air paleotemperatures, performed on the basis of data of isotope-oxygen composition of ice from the veins, did show that at the period between 11 and 6 cal Ka BP, the mean winter air temperature on the Daurkin Peninsula was by 2–5 oC lower than today, but the air temperature of the coldest month (January or February) was still lower (by 4-8 oC) than today. The noticeable trend of increase of stable isotope values in the ice veins from early Holocene to the present time is indicative of a steady positive trend of mean winter air temperatures in the Holocene

Two approaches to hydrograph separation of the glacial river runoff using isotopic methods

Application of the stable isotope method in the balance equations used to calculate separation of the runoff hydrograph from the Djankuat Glacier basin is demonstrated. Simultaneous solution of equations of water, isotope and ion balances is applied to estimate contributions of different components and processes to formation of the Djankuat River runoff regime. For June 2014, we made calculations for the purpose to separate contributions of the spring (isotopically weighted) snow and winter (isotopically depleted) snow. Field works in the glacial basin Djankuat were performed during two ablation seasons, i.e. from June to September of 2013 and 2014. Two approaches were used when calculating separation of the runoff hydrograph by means of solution of systems of equations for isotopic and ion balances: 1) taking account of the isotope fractionation during snow melting, and 2) with no account for the fractionation. Separation of the hydrograph for June 2014 have shown that about 15–20% of the Djankuat River runoff is formed by spring snow melting, sometimes increasing up to 36%. Contribution of spring meltwater to the total runoff increases when the isotope fractionation during the snow melting is taken into account for the calculations. In this case, the contribution of spring snow changes from 30 to 50%