Multi-scale Analysis Of Asian Monsoon Changes In The Past 640ka

Multiple analysis of variation of Monsoon and its forcing mechanisms are the hot spots in the research of paleoclimate.As a typical monsoon system,Asian Monsoon system plays a key role in the circulation of global water vapor and energy.The high-resolution and precisely-dated stalagmite record from Chinese caves has extended to the past 640 ka,which provides a new insight to study the multiple analysis of variation of Asian Monsoon.The empirical mode decomposition(EMD)method is used to re-analyse the features,contributions and driving forces of the sequence in the orbital and millennial time scales.The Results are as follows.On the orbital timescales,four dominant periodicities are 11.6 ka,23.3 ka,42.4 ka and 95.5 ka,among which the precession and semiprecession band oscillations are the most prominent periodicities,with contribution rates of 31.1%and 30.7%,respectively;the cross-spectrum analysis of the semiprecession component and bi-hemisphere insolation(BHI)are strongly correlated,indicating an amplified response of precipitation and temperature variability to the interhemispheric insolation in the low-latitude regions,thus further affecting the intensity of the Asian Monsoon.On the millennial timescales,obvious oscillations at the 5 ka and 1-2 ka bands roughly correspond to the classical Bond and Dansgaard-Oeschger(DO)cycles.And the Ca/Sr sequence from the North Atlantic and IRD sequence from the ODP site 980 also show dominant 5 ka and 1-2 ka periods.Additionally,a strong correlation is found between the detrended stalagmite ?18O records and Ca/Sr sequence(especially at the 5 ka band).This result means that the 5 ka cycle is characteristic of the glacial-interglacial cycle since the middle and late Pleistocene and may imply that climate change on the millennial timescale is the result of an interaction between global ice volume and insolation.