VARIATIONS IN A HYDROLOGICAL CYCLE AT THE LAKE LADOGA CATCHMENT AND THE NEVA RUNOFF IN THE 20TH AND 21ST CENTURIES AS ANALYZED BY A GLOBAL CLIMATE MODEL

K. Arpe, A. M. Obukhov, L. Bengtsson, G. S. Golitsyn, L. K. Efimova, I. I. Mokhov, V. A. Semenov, and V. Ch. Khon

The Neva runoff and the hydrological cycle of the Lake Ladoga catchment are analyzed with the empirical and modeling data. A coupled sea—air general circulation model ECHAM4/OPYC3 was used to calculate the mean value, the annual course of water balance, and typical interannual variations in the Neva runoff since the mid-19th century and to estimate their variations in the 21st century, taking into account anthropogenic variations due to increasing concentration of greenhouse gases in the atmosphere. Against the background of significant year-to-year and decadal variations, the model calculations revealed a general growth of precipitation over the Ladoga catchment and of the Neva runoff in the 21st century. A tendency is found toward the extending range of variation in the regional hydrological cycle, including the Neva runoff, in the 21st century.