Factors Influencing Changes of the Initial Stable Water Isotopes Composition in the Seasonal Snowpack of the South of Western Siberia, Russia

Abstract

Stable water isotopes in snowpack and snowfalls are widely used for understanding hydrological processes occurring in the seasonally snow-covered territories. The present study examines the main factors influencing changes of the initial stable water isotopes composition in the seasonal snow cover of the south of Western Siberia. Studies of the isotopic composition of snow precipitation and snow cover, as well as experiments with them, were carried out during two cold seasons of 2019–2021, and laser spectroscopy PICARRO L2130-i (WS-CRDS) was used for the determination of water isotope composition (δ18O and δD). The main changes in the isotopic composition of the snow cover layers in the studied region are associated with the existence of a vertical temperature gradient between the layers and with the penetration of soil moisture into the bottom layers in the absence of soil freezing. During the winter period, the sublimation from the top layer of snow is observed only at the moments of a sharp increase in the daily air temperature. At the end of winter, the contrast between day and night air temperatures determines the direction of the shift in the isotopic composition of the top layer of snow relative to the initial snow precipitation.

Impact of Snowmelt Conditions on the Isotopic Composition of the Surface Waters of the Upper Ob River during the Flood Period

“…Figure 2 shows that the isotopic composition of the water in the Ob River begins to become lighter due to snowmelt more than a week before the ice drift, and the sharpest change in the isotopic composition was observed in the spring of 2021, although a rise in the water level and an increase in water discharge were noted earlier in 2020 [37,43,44]. In our opinion, these differences can be associated with the conditions of snow accumulation, the main characteristics of which are given in Table 2 for the winters of 2019-2020 and 2020-2021.…”

“…It is known that the snow cover of temperate and polar latitudes as a whole determines the integral seasonal (for the winter period) characteristics of the isotopic composition of moisture entering the study area [36,37]. For the watersheds of a cold climate, the contribution of winter precipitation to the water runoff occurs only from the beginning of the snowmelt period; therefore, the bulk snowpack sampled just before the snowmelt is a convenient object for studying the distribution of winter snowfalls over the catchment area.…”