Te isotopic characteristics of the pingo ice cores are considered. Te distribution of δ18O and δ2H values, dexc, δ18O–δ2H and δ2H–d exc relationships, and the simulation of the distribution of δ18O and δ2H values during the ice formation in a closed system, allowed drawing conclusion about the hydrological conditions and stages of the ice core growth. All pingos (Pestsovoye, Weather, Pingo-20) were formed in draining lake basins in the course of freezing of closed taliks. It is established that the water, which served as a source for the formation of the ice core, was subjected to evaporation still before the ice formation. According to our estimates, the water from which the ice of the Pestsovoye pingo was formed was heavier in values of δ18O and δ2H by 3.9 and 29.7‰, respectively, than the current average annual precipitation in the region. Similarly, for the ice of the core of the Pingo Weather it is 2.9 and 14.5‰, and 5.1 and 27.7‰ for the Pingo-20, respectively. In the ice cores of all considered pingos there is an ice formed in a closed system: in Pingo-20 it is a pure injection ice, while in the Pestsovoye and the Weser ones – the injected-segregated ice. Te frost mounds Pestsovoe and Weser grew under changing hydrological conditions: one part of the ice was formed when there was a free flow of water to the freezing front (open system); the other one – when the water-saturated lenses of the closed talik were frozen (closed system). Te isotopic composition of ice being formed under conditions of a closed system reflects isotopic depletion during freezing and ice formation according to the Rayleigh model. It is expressed in a successive decrease in the values of δ18O and δ2H from the frst portions of ice to the last ones as the freezing continued. Te contrast values of δ18O and δ2H in different parts of the ice being formed in the closed system may be used as an additional tool to identify direction of freezing. In a closed system, the last portions of ice have the greater contrast of the isotope values as compared to the frst portions.

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%.

Байкал, снежный покров, стабильные изотопы кислорода и водорода. Baikal, snow cover, stable isotopes of oxygen and hydrogen. Стабильные изотопы водорода и кислорода-природные трассеры гидрологического цикла, которые используются в исследованиях гидрологических процессов и для нахождения источника влаги. В статье приводятся данные по снежному покрову Трансбайкальского региона от г. Якутск до озера Байкал. Улан-Удэ был выбран в качестве ключевого участка для более детального изучения снежного покрова. Показано, что в зимний период значения δ 18 O снега в г. Улан-Удэ достигают −39‰, что типично для внутриконтинентальных воздушных масс-результатов меридионального и западного переноса. Цель статьи-описать пространственную изменчивость содержания стабильных изотопов водорода и кислорода в снежном покрове. Deuterium and oxygen-18 are standard water tracers which are widely used to investigate hydrological processes and to trace the moisture sources. In this study, we collected bulk samples taken from the snow cover in the Baikal region distributed from the city Yakutsk to the Lake Baikal. Ulan-Ude had been chosen as a key site to study the snow cover in more details. It has been shown that during the winter season δ 18 O values in Ulan-Ude reach −39‰ that is typical for the inland air masses of meridional or western transport. The aim of this study was to describe the spatial variability of concentrations of the isotopes deuterium (2 H) and oxygen-18 (18 O) in the snow cover.

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