Holocene Dynamics of the East-Asian Monsoon in the Lower Amur Area

Аннотация

The spatial and temporal dynamics of monsoon in the Holocene has been reconstructed for the Lower Amur area. Four stages of cooling are determined (10300–10800, 8000–8300, 4200–4600 and 2500 yrs. ago). During these periods the intensity of the summer monsoon was weakest. The conventional northern boundary of monsoon influence moved from 54 to 48o N. Two retrospective scenarios of the interaction versions of interaction of seasonal atmospheric centers are suggested, which had influence on the dynamics of the cyclone process over the southern part of the Far East in the Holocene. The cyclones attenuated as a result of frequently recurring long-lasting periods of an increase in pressure in the region of the summer Far-Eastern and Asian depressions, and a decrease in pressure over the Sea of Okhotsk as well as the displacement of the center of the Okhotsk anticyclone toward southern latitudes, which was often in a quasi-stationary state blocking the passage of cyclones to the southern coast of the Sea of Okhotsk. In either case, the cyclones were forced away to lower latitudes and intensified over northern and eastern regions of China. The two scenarios could work both synchronously and metachronously.