Modern Dynamics of River Runoff in the Cryolithozone. Part 2. Formation of River Runoff

In regions where permafrost (PF) is widespread, which make up the cryolithozone, the processes of runoff formation acquire exceptional specificity and complexity due to the presence of frozen soil. In the context of observed climate change leading to the degradation of the permafrost zone, understanding the mechanisms of river runoff formation in these regions becomes an important task. The article analyzes the characteristic features of the regime and the main factors determining the spatiotemporal variability of runoff. The water regime of the rivers in the permafrost zone is characterized by a pronounced spring flood, formed due to the melting of the snow cover on a practically impermeable frozen bed, relatively low summer–autumn floods, and a stable, but pronounced winter low-water season; the rivers are fed mainly by subpermafrost waters via through taliks. The nature and mechanisms of changes in the water regime are influenced by a number of climatic and landscape factors, as well as the continuous permafrost distribution in the basin. The main mechanisms of change include an increase in the thickness of the seasonally thawed layer (STL), expansion of taliks, and increased lateral groundwater flow.