Vol 44, No 10 (2019)

The paper analyzes long-term changes in the water inflow to Lake Baikal which have occurred since the early 20th century and have been transformed due to the global warming intensification since the 1970s. The differences in distribution parameters and in the values of the inflow of estimated probabilities are studied for the full series and for its two parts divided as of1971. The revealed increase in the wintertime inflow is caused by the cold period duration reduction and by the permafrost degradation resulting from the air temperature rise. Since 1996 inflow has decreased, which is associated not only with precipitation reduction but also with evaporation increase. The Selenga River, the largest tributary of Lake Baikal, demonstrates the greatest decrease in runoff among the Baikal rivers.

The monitoring, field, and satellite datasets are used to estimate changes in suspended sediment budget for the Selenga and Upper Angara river deltas. Sediment deficit during recent decades dominates delta evolution due to decrease in the sediment delivery to the delta since the middle of the 1970s by 51% for the Selenga River and by 70% for the Upper Angara River. The observed decline in the sediment runoff and peak water flows associated with the sediment deposition within the inundated flood-plain of the deltas leads to the reduction of the sediment aggradation rates over both deltas. Under low water flows we observed longitudinal increase of the sediment transport rates along Selenga River delta; the Upper Angara constantly reduces sediment transport rates under various hydrological conditions.

The impact of modern climate change on lakes is one of the most relevant problems in the field of limnology. For Lake Baikal this impact is manifested in the change in abiotic characteristics of the lake ecosystem. It is shown that the pattern of modern climate change in the Baikal region includes both the “secular” warming trend and the intrasecular variations which exceed this trend in the scale and may be caused by atmospheric circulation. The effect of atmospheric circulation is associated with the physiographic characteristics of separate parts of the lake and its watershed. The influence of changes in atmospheric circulation on the ice and thermal regime of Lake Baikal is analyzed for the period of 1950–2017 for which objective analysis data on the large-scale atmospheric circulation in the Northern Hemisphere are available.

The paper studies the connection between the precipitation regime over the northern Baikal mountain region during the warm season (April–October) and atmospheric macrocirculation processes, the results are presented. Based on the data of ten weather stations, spatiotemporal heterogeneities in the precipitation regime are revealed for the period of 2000–2018. The long-term (since the middle of the 1960s) trends in total precipitation are evaluated. According to the analysis of HYSPLIT five-day backward trajectories (for days with precipitation), the main directions of moisture transport to the study area are identified, and the trajectories are typed for each month. Three groups of atmotpheric macroprocesses which induce precipttation are identified, and the contribution of each group to total precipitation is estimated. The spatial distinction between different parts of the study area in the precipitation regime and predominant moisture sources is found.

The dynamics of multiyear mean thermal conditions in the 3.2-m soil layer in Transbaikalia is studied. A high correlation between variations in air temperature and soil temperature is revealed for summer, and low correlation is found for winter. The trends in cumulative soil temperature during the positive and negative temperature seasons are identified. The sum of negative soil temperatures at the depth of 80 cm exhibits an increasing multiyear trend. In cold seasons, the linear trends in soil temperature are stronger as compared to air temperature trends.