HYDROLOGICAL REGIME IN SIBERIAN RIVER BASINS: MODEL ESTIMATES OF CHANGES IN THE 21ST CENTURY

I. I. Mokhov and V. Ch. Khon

Characteristics of the hydrological regime are analyzed for Siberian river basins, including regional precipitation and runoff of the Ob, Yenisei, and Lena rivers. Using coupled ocean–atmosphere general circulation models ECHAM4/OPYC3 and HadCM3, runoff variations are simulated for the period since the mid-19th century, and their changes in the 21st century are estimated with consideration for possible anthropogenic impacts due to greenhouse gas increase in the atmosphere. Similar regional estimates are also made by using the IAP RAS global climate model of intermediate complexity. On the whole, against the background of significant interannual and decadal variability, the model calculations predict a general increase in river basin precipitation and river runoff, which is particularly considerable for the Lena River. Some decrease in runoff of the rivers Ob and Yenisei in the first half of the 21st century is also possible. A tendency for an increase in the range of model interannual variations in regional characteristics of the hydrological cycle is found. Model and empirical estimates are obtained for a relation between Siberian river runoff variations and changes of atmospheric circulation conditions, including the North Atlantic and Arctic Oscillation indices and characteristics of centers of action of the atmo¬sphere, in particular of the Siberian anticyclone.