Isotope-geochemical investigation of glacio-nival systems of the Tabyn-Bogdo-Ola mountain massif (Western Mongolia)

Results of investigation of glacio-nival systems made in the Tabyn-Bogdo-Ola mountains (Western Mongolia) are presented in the paper. Average content of δ18О in the Tsagan-Us river water amounts to 17.44‰ that is almost equal to the isotope content in the clear glacier runoff near the edge of the Kozlov Glacier (−17.43‰). It means that the isotope content in water doesn’t significantly change over a distance of 30 km along the Tsagan-Us river. Hence, it appears that for this distance the river has no additional non-glacial feed. The magnitude 17.4±0.1‰ can be considered as the average content of isotopes in the glacio-nival system in the Tabyn-Bogdo-Ola mountain massif. This value can also be the precipitation-weighted average isotope content in the solid precipitations which are accumulated in glaciers of this massif. Seasonal isotope fluctuations are partly preserved in the snow-firn mass in the accumulation area of the Kozlov Glacier. A rate of annual accumulation was estimated by multiplying the apparent thickness (160 cm) of an annual layer into the snow density. According to our observations, it is equal to 800 mm w.e./year during 2013–2014. Accumulation is increased due to the wind and avalanche transportation of snow. During the ablation season, summer and spring snowfalls over the Kozlov Glacier area melt. Thus, it is possible to suppose that the autumn snowfalls play the important role in the accumulation. We may also suppose that the main source of the moisture for the Tabyn-Bogdo-Ola massif is located somewhere in the Inner Asia.