Preliminary study on the summer monsoon climate of Chinese Loess Plateau during the last interglacial period

摘要

Research on long-term climatic variation on the Chinese Loess Plateau has demonstrated that loess is mainly the dust deposits transported by the northern wind of the winter monsoon, and that the paleosol accreted by rather slow dust accumulation was closely related to a strengthened summer monsoon. The climate over the Chinese Loess Plateau during the last glacial period is characterized by strong summer monsoon circulation accompanied by relatively weak winter monsoon, during which a triple paleosolcomplex (S1) was developed. Proxy index variations such as magnetic susceptibility and particle size reveal the variational history of the summer and winter monsoons. Thus, it is quite possible to reconstruct the climatic pattern of the Loess Plateau inthe last interglacial period by measuring S1 paleosol sections for specific climatic indices all over the plateau. Furthermore, transform equation enable us to quantitatively reconstruct the climatic pattern of the period. For this purpose, 24 high-resolution sections along three main section lines of the last interglacial paleosol were sampled and the susceptibility was measured (fig. 1). By regression analysis between modern soil susceptibility and the present climate parameter data at 104 locations,the best fit regression functions were developed for annual mean temperature and precipitation. Consequently, annual temperature and precipitation have been calculated for the last interglaciation using the transforming equations. The northern boundaries of the summer monsoon front before as well as after the last interglacial period are also discussed.