Winter and summer monsoonal evolution in northeastern Qinghai-Tibetan Plateau during the Holocene period

Climate change especially moisture condition in the northeastern Qinghai-Tibetan in China are mainly controlled by the strength and variability of Asian winter and summer monsoon. In this paper, we presented the climate record and related winter and summer monsoonal history in Gonghe Basin, northeastern Qinghai-Tibetan Plateau, based on the geochemical indicators (geochemical elements content, i.e., Fe2O3, CaO, Zr and Sr content, and geochemical parameters, i.e., the chemical index of alteration (CIA), Zr/Rb, Rb/Sr, CaO/MgO, SiO2/TiO2 and SiO2/(Al2O3 + Fe2O3) ratio) of the peat deposits and 14C and OSL technologies. The regional temperature and humidity gradually increased in 10.0-8.5 cal ka BP, accompanied by enhanced summer monsoonal strength and decreased winter monsoonal strength. But climate became cold and dry between 8.5 cal ka BP and 7.6 cal ka BP owing to the stronger winter monsoon. During the 7.6-3.8 cal ka BP, stronger summer monsoon and weaker winter monsoon led to an optimal warm and humid condition, although it had several cold phases. From 3.8 cal ka BP to 0.5 cal ka BP, the regional climate tended to be cold and dry, with increasing winter monsoonal strength and decreasing summer monsoonal strength. Thereafter, the relatively warm and humid climate appeared again, due to the stronger summer monsoon. That is to say, the regional climate conditions are mainly related to the winter and summer monsoonal changes. These changes are consistent with palaeoclimatic records (monsoonal model) from the region influenced by the Asian monsoon in eastern China. In addition, nine cold events were recorded: 8.5-7.8 cal ka BP, 6.1-5.6 cal ka BP, 5.2-4.8 cal ka BP, 4.7-4.3 cal ka BP, 4.1-4.0 cal ka BP, 3.8-3.4 cal ka BP, 3.0-2.3 cal ka BP, 1.4-1.3 cal ka BP, and 1.0-0.5 cal ka BP, which are coincident with cold fluctuations in the high and low latitudes of the Northern Hemisphere on a millennial scale, as recorded by lakes, peat sediments, and ice cores in the Qinghai-Tibetan Plateau. In conclusion, Holocene millennial-scale climatic changes in Gonghe Basin were controlled by the dual function of Asian monsoonal changes and global cold fluctuations.