Statistical-dynamical retrieval and driving mechanism study of monsoon variation over East Asia in the last millennium

A nonlinear statistical-dynamical model of the East Asian monsoon is established using observed data. The model is applied to quantify individual contributions of different factors, which provide a quantitative reference for the study of the driving mechanism of East Asian monsoon. Results show that:(1) The East Asian monsoon is a complex nonlinear dynamic system influenced by many factors over the past thousand years. Some factors are driving forces and others are feedback regulations. Interactions among these factors are coupled with the East Asian monsoon; (2) The monsoon driving forces mainly come from sea surface temperature over the subtropical Pacific, the Tibetan Plateau thermal forcing, the coupling interaction mechanism of CO₂ and N₂O, solar radiation and N₂O cross-terms, CO₂ and CH₄ cross-term. Regulation effect is mainly from the location of continent by stalagmite δ¹⁸O, CO₂ concentration, changes in solar radiation, the coupling interaction mechanism of CH₄ and N₂O, solar radiation and ENSO cross-term, stalagmite and CH₄ cross-term. The concentrations of greenhouse gases (CO₂, CH₄ and N₂O) have a great contribution to the driving force and regulating effects of the East Asian monsoon; (3) It is inferred from the dynamic retrieval mechanism that the subtropical Pacific and the tropical western Pacific have driving effects on the East Asian monsoon. The main driving force comes from subtropical Pacific, which indicates that the main driving source of East Asian monsoon changes is in the subtropical Pacific Ocean, and the secondary source is in the tropical western Pacific Ocean; (4) Stalagmite δ¹⁸O mainly refers to the features of summer monsoon contributed by sea-land temperature to monsoon evolution.