干旱区生态环境知识资源中心

Former shorelines and sedimentary records from several lake basins in northwestern China (Xinjiang, Qinghai) give evidence for warm and humid climatic conditions during 40-30 ka BP. Further indications of this favorable climate period are derived from palaeosols from the Ili loess and from cemented calcareous layers on the terraces of the Keriya River at the southern margin of the Tarim Basin and in the Badain Jaran Desert in Inner Mongolia. At that time, annual mean temperature in the Qaidam Basin was 2degreesC higher and in the western part of Inner Mongolia even 2-3degreesC higher than today. Precipitation in most parts of northwestern China was between 60-300 mm greater than today. These changes were probably a consequence of an increase in ocean surface temperature and evaporation resulting from a higher radiation input at middle and low latitudes caused by changes in the Earth’s precessional cycle. As a result of these orbital changes, it is suggested that the intensified westerly circulation was responsible for increased moisture over northwestern China. (C) 2004 Elsevier Ltd. All rights reserved.