Impacts of Hydro-Climatic Change, Permafrost Thaw and Industrial Pressures in the Lake Baikal Drainage Basin (Mongolia and Russia)

Abstract:

The large Arctic river Yenisei and Lake Baikal with its unique ecosystem containing endemic species are influenced by on-going hydro-climatic changes in the Lake Baikal Drainage Basin. The latter extends from southern Siberia into northern Mongolia, and contains one of the word’s larger mining regions, for instance with mining of gold, silver, copper and coal. Recognizing that changing hydro-climatic conditions in the basin may lead to changed loading pattern of anthropogenic substances to Lake Baikal and Yenisei, we aim at identifying long-term historic and projected future hydro-climatic trends in this basin and their (possible) impacts. The analyses are based on hydro-climatic observations and the output 22 Earth System Models (ESMs) of the Coupled Model Intercomparison Project, Phase 5 (CMIP5). Observations show that warming rates of the basin were twice as high as the global average during past 70 years. Decreased intra annual variability of river discharge over this period indicates basin-scale permafrost degradation. CMIP5 ensemble projections show further future warming, implying continued permafrost thaw. Most individual models as well as the CMIP5 ensemble mean result indicate increased runoff in the future. However the spread of individual model results is large. Parallel results show that such increased runoff can considerably increase the annual riverine sediment loads and consequently the loading of contaminants that are attached to the sediments, in particular downstream of mining sites. More generally, this exemplifies how long-term hydro-climatic changes, permafrost thaw, and industrial pressures may interact in increasing the bioavailability of contaminants in downstream recipients.