末次冰消期东亚季风区西北缘气候快速变化事件

Rapid Climate Changes at Northwestern Margin of East Asian Monsoon Region During the Last Deglaciation

通过对中卫剖面和米浪沟湾剖面的年代学与高分辨率气候地层记录的研究,认为末次冰消期东亚季风区西北缘发生气候快速变化事件,它可分辨出古仙女木、波令、老仙女木、阿勒鲁德、IACP 和新仙女木等6个气候阶段,并可与格陵兰冰心(GISP2)检出的6个气候阶段相对比。气候快速变化事件以快速变化、不稳定、多波动为特征,表现为冷干—暖湿—冷干—凉湿—暖干—冷干—冷湿的交替变化。冰消期冬、夏季风有较为复杂的消长关系,冰阶时二者互为消长,间冰阶时并不完全互为消长。冬季风在波令和阿勒鲁德暖期较新仙女木冷期强盛,这是北半球高纬度海区海冰面积在暖期缩小、冷期扩大而影响亚洲大陆蒙古—西伯利亚高压暖期增强、冷期减弱的结果;夏季风则与格陵兰冰心δ^(18)O 的变化具有一致性,其强弱与北半球高纬地区有紧密联系,这种联系可能不是通过季风锋面降水带建立起来的,而可能是海冰面积变化导致厄尔尼诺—南方涛动(ENSO)爆发造成的。

Through the researches of the chronology, the high-resolution climatic and stratigraphic records of the Zhongwei section and Milanggouwan section. The rapid climatic changes occurred at the northwest margin of East Asia monsoon region during the last deglaciation were divided into six climatic periods, namely Oldest Dryas, Exiling, Older Dryas, Allerd, IACP and Young Dryas periods. They can be comparable with the six climatic stages recorded in Greenland ice core (GISP2). The rapid climatic changes were characterized by their fast alterations and instability and manifested in the fluctuated alternation from cold-dry to warm-humid to cold-dry to cool-humid to warm-dry to cold-humid climates. During the last deglaciation winter and summer monsoon were complex. During the stadial summer monsoon and winter monsoon alternately strengthened and weakened, but during the interstadial this might not be the case. Winter monsoon were stronger in the B/A warm period than in the YD cold period. The reason for this is that the sea ice cover in the high-latitude seas of the Northern Hemisphere shrank in warm period and enlarged in cold period, as a result, the Mongolian -Siberian high over the Asian continent was reinforced in warm period and weakened in cold period. Summer monsoon intensity roughly coincided with the δ18O record of Greenland ice core and was closely related to the high-latitude region of the Northern Hemisphere. However, such linkage may not be established by the monsoon frontal precipitation, instead it may be caused by ENSO outburst due to the changes in sea ice cover.