The Special Warm-Humid Climate and Environment in China during 40～30 ka BP:Discovery and Review
SHI Ya-feng,ZHAO Jing-dong(State Key Laboratory of Cryospheric Sciences,Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences,Lanzhou Gansu 730000,China)
The period of 40~30 ka BP was regarded as an interstadial of the Last Glaciation in the previous studies,when temperature was slightly increased,but still in glacial period.An unknown interglacial period,the temperature was about 4 ℃ higher than that at the present,was first obtained on the basis of the Guliya ice core studies.Considering the records from lacustrine sediments,pollen and macrofossils,paleosol in loess and desert sections,stalagmites in karst caves,ancient water course in North China Plain,oceanic deposits in the coastal areas and sea level changes,it is revealed that precipitation during 40~30 ka BP was higher than that at the present in the whole China,and large fresh water lakes occurred in the Tibetan Plateau and the arid areas in Northwest China,enlarging the external drainage areas,such as the water system of the upper reaches of the Yellow River in Qinghai Province came into being.Forest belt expanded northwards and westwards under the warm humid climate at that time.The Dacrydium sp.that lives in the warm and humid climate in the tropical areas in the South China,expanded to 22°~24° N,which indicated that temperature during 40~30 ka BP was about 2 ℃ higher than that at the present,and precipitation also increased.The stalagmite records from the lower reaches of the Yangtze River and the flora,paleosols,fluvial sediments in the semi-arid and semi-humid regions in North China indicated that precipitation increased and forest area enlarged.Large transgressions occurred in the western coasts of Bohai and delta areas of the Yangtze River and Pearl River due to mountain glaciers and ice sheets in the polar areas retreating,sea level rising and the subsidence of these areas.The special warm humid climate in China has a strong relationship with the higher July insolation in the mid and low latitudes during 40~30 ka BP as compared with that in today,which was mainly due to the change in the perihelion of the orbital parameters.Higher July insolation caused temperature rising and precipitation increasing in monsoon and westerly areas,and the improved vegetation has a positive feedback to the temperature and humidity.
【Fund】： 国家自然科学基金项目(40501007);; 中国科学院知识创新工程重要方向性项目(KZCX2-YW-301);; 国家重点基础研究发展计划(973计划)项目(2007CB411500);; 科技部科技基础性工作专项项目(2006FY110200)资助
【CateGory Index】： P343.6
【CateGory Index】： P343.6