黄土高原100万年以来东亚夏季风演变信号的多尺度分析

Significant Multi-scale Analysis on Evolution of the East Asian Summer Monsoon on the Loess Plateau during the Last 1 MaB.P.

在研究黄土高原东亚季风地质时期周期演变中，利用经验模态分解（EMD）方法对黄土高原甘肃省灵台和赵家川黄土剖面约1MaBP．以来磁化率时间序列进行多尺度变化分析，结果表明：1）0～0．8MaKP．地球轨道三要素中的偏心率准400ka、100ka周期在黄土沉积中反映明显，方差贡献率达35．19％，还发现16ka的岁差周期及334ka、177ka、58ka、31ka、7．9ka、3．9ka的非轨道准周期；2）0．8-1MaB．P．也发现地球轨道三要素中的偏心率准100ka周期、21ka岁差周期及55ka、8．3ka、3．5ka非轨道准周期，偏心率准100ka周期具有主导地位（方差贡献率达37．44％）；3）尽管黄土记录的东亚夏季风100ka周期的产生机制已有多种假说，古气候学界还是普遍认为它产生于某些尚不清楚的过程，有待进一步研究。

China＇s loess--palaeosoil sequence is not only the continuous record of Quaternary palaeoclimatic evolution but also the product of East Asia monsoon. Signals on Magnetic Susceptibility （MS） recorded in the Loess Plateau reflect the long-term evolutional information of East Asian summer monsoon. In this paper, time series of Magnetic Susceptibility （MS）（since 1 MaB. P. ） recorded in the given section of Loess Plateau which are located in Lingtai and Zhaojiachuan in Gansu Province was analyzed using EMI）. The results showed that： 1） During the period of 0～0. 8 MaB. P. ,quasi 400 ka and quasi 100 ka cycles, elements of Earth orbital three eccentricity-ratio cycles, are discovered evidently in the loess deposition, and their variance contribution rate is up to 35.19%. As a result, it is safe to draw a conclusion that the quasi 100 ka cycle fluctuations play leading role to East Asian summer monsoon during 0～0. 8 MaB. P.. In addition, cycle quasi 16 ka and non-orbital cycles including quasi 334 ka,quasi 177 ka,quasi 58 ka,quasi 31 ka,quasi 7.9 ka and quasi 3. 9 ka were found as well. 2） During the period of 0. 8 ～ 1 MaB. P. , quasi 100 ka cycle, element of Earth orbital three eccentricity- ratio cycles, 21 ka precession cycle, non- orbital cycles including quasi 55 ka, quasi 8. 3 ka and quasi 3. 5 ka were also found. During this period, variance contribution rate of quasi 100 ka cycle is up to 37. 44% ,and quasi 100 ka cycle has a leading role. 3） Although there are a variety of hypotheses on the mechanism of 100 ka cycle of the East Asian summer monsoon recorded in loess, some unclear processes on it are believed universally in the palaeoclimatic scholars. As a result, more research work is still needed to be done for research work further.