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Based on simulations with an ensemble of CMIP6 (Coupled Models Intercomparison Project, phase 6) climate models using Bayesian averaging, an analysis of changes in the runoff of a number of Russian rivers—the Volga, Ob, Yenisei, Lena, Amur, and Selenga—has been carried out this century. Bayesian weights take into account the skill of runoff reproduction by models (long-term average runoff, linear runoff trend over a time interval with available runoff observations, and interannual and interdecadal variability). The skill of reproduction of runoff characteristics by individual CMIP6 ensemble models varies most widely for long-term average runoff; runoff trend; and, to a lesser extent, interannual variability. In the 21st century, the ensemble average runoff increases for most of the analyzed rivers, with the exception of the Volga. This increase is more pronounced in scenarios with large anthropogenic impacts. It is especially significant for the SSP5-8.5 scenario (Shared Socioeconomic Pathways, 14 5-8.5), in which the trend of increase in runoff in 2015–2100 relative to its modern long-term average value is (10 ± 4)% for the Ob, (16 ± 3)% for the Yenisei, (39 ± 7)% for the Lena, (36 ± 7)% for the Amur, and (18 ± 6)% for the Selenga. The main reason for changes in ensemble average runoff in the 21st century in models under all SSP scenarios is the changes in precipitation. Accounting for differences in model skill when reproducing river runoff on average for 2015–2100 reduces intermodel deviations relative to the corresponding values when uniformly weighting the model calculation results by 6–26%, depending on the SSP scenario and river catchment. [ABSTRACT FROM AUTHOR]

The results of morphological and genetic analysis of populations/forms/species of the pidschian-like whitefishes from the middle and lower streams of the Lena River and adjacent rivers are presented. There are good grounds to believe that despite considerable heterogeneity of whitefishes in Siberia, a small number of stable forms/species live in the waterbodies of the Siberian Arctic. These are the East Siberian whitefish (C. lavaretus pidschian n. brachymystax), glacial—plain whitefish (C. lavaretus pidschian n. glacialis) and Yukagir whitefish (C. lavaretus pidschian n. jucagiricus), as well as their hybrid populations. The glacial—plain whitefish and its derivatives differ from the East Siberian whitefish in plastic traits but they are identical in meristic ones. Molecular genetic studies showed that, in most cases, glacial—plain whitefish formed vast loosely connected haplotype networks, which corresponded to the long-term population existence in favorable conditions. Haplotypes of the East Siberian whitefish are closely related to the haplotypes of whitefish forms/species from the waterbodies of Southern Siberia, characterized by radial structure of median-joining network. Such network structure indicates a recent decline in the East Siberian whitefish numbers with subsequent expansion, which is directly associated with the Quaternary glaciation events. [ABSTRACT FROM AUTHOR]

The hydrological models ECOMAG and HBV were used to calculate the characteristics of river flow and snow Water Equivalent in the Lena River basin. The input data included the meteorological observations and the results of calculations with global climate models with the implementation of scenarios of natural climate conditions, taking into account the anthropogenic effect on climate. The calculations were made for a historical period (1970–1999) and up to the end of the XXI century. Hydrological models for several hydrometric gages in the Lena basin were calibrated and verified. The simulation of the annual and seasonal runoff using the climate model data was evaluated by comparison with observation data. According to the results using numerical experiments over the historical period, the increase in the Lena runoff is mostly due to natural climate variations. Conversely, in the XXI century, the anthropogenic climate changes determine the specific features of the regime of river runoff and snow cover. The warming caused by an increase in greenhouse gas concentrations in the atmosphere leads to an increase in snow water equivalent and transformation of the hydrological regime in the area, in particular, to an earlier beginning of active snow melting (up to two weeks) and higher maximal discharges during spring flood. At the same time, the volume of runoff decreases in the summer and increases in the autumn and winter. [ABSTRACT FROM AUTHOR]

Permafrost degradation has led to increased riverine ion concentrations and export to the sea. This study uses major ion data collected in summer in 2012 and 2013 and during spring flood in 2015 to investigate the spatio-temporal variability in chemical weathering patterns and the associated CO 2 consumptions in one of the major Arctic Rivers – the Lena River and its tributaries. The catchment shows strong spatial variations in major ion concentrations in the main river and tributaries. The weathering flux represented by TIS (total inorganic solids) is calculated to be 112 Tg/yr, which is almost double that calculated in an earlier study 20 years ago for the same region. The CO 2 consumption is estimated to be 4.9 Tg C/yr, which is approximately equally shared between weathering of carbonates and silicates, despite two thirds of TIS derived from carbonates and the rest of TIS by silicates and evaporites. Our results suggest an enhanced role for silicate weathering in elemental export and CO 2 drawdown due to the ongoing transition from a near surface-dominated system towards a deep groundwater dominated system caused by permafrost degradation in the Arctic region under a warmer climate. Such an enhanced weathering pattern is also expected in other Arctic rivers; hence, a re-evaluation of the weathering budgets is clearly needed. Our findings improve our understanding of the response of the weathering regime in large Arctic river catchments to ongoing climate-driven permafrost loss, which also sheds lights into the role of land-sea element fluxes in sustaining primary production and carbon cycling on the Arctic shelf seas. [ABSTRACT FROM AUTHOR]

This paper studies the possibility of using the WaTEM/SEDEM model to assess sediment yield from the catchment area within the Lena River catchment. The study was carried out based on a comparison of predicted data and measured data of the suspended sediment yield at the gauging stations of the state monitoring network of Russia. The study was performed within two areas, with plain and mountainous relief. The first site is located within the catchment area of the river Chara with an area of 4150 km2. The second site rests on the catchment area of the Lena River between the Tabaginskiy and Kangalassky capes near Yakutsk city. The catchment area of this site is 15,740 km2. The values of sediment yield from the "Yakutsk" catchment area are in much better agreement with the values of the measured sediment yield values than in the "Chara" catchment area. The predicted sediment yield from the study area remained almost unchanged from the period 1986–2019 and amounted to 3.5 t/km2, while the suspended sediment yield in the Lena at the Tabaga gauging station slightly increased from 7 to 9.45 t/km2 per year. [ABSTRACT FROM AUTHOR]