CLIMATIC CHANGES SINCE THE LATE PLEISTOCENE IN DESERTS OF NORTHERN CHINA
Dong Guangrong Jin Jiong Gao Shangyu Li Baosheng Chen Huizhong (Lanzhou Institute of Desert Research, Chinese Academy of Sciences)
Basing on the analyses of stratigraphy and sedimentary facies, the climatic changes since the late Pleistocene in deserts in Northern China may be concluded as follows: (1) Deserts in China are divided into two Areas, Area-Ⅰ and Area-Ⅱ. The sequence of climatic changes in Area-Ⅰ is different from that in Area-Ⅱ. Area-I consists of Gonghe Sandyland in Qinghai, sandylands around Qinghai Lake, Mu Us Sandyland on Ordos Plateau, Otingdag Sandyland, Horqin Sandyland, Hulun Buir Sandyland, Gurban Tonggut Desert, and the sandyland at the lower reaches of Nen Jiang River, and also some part of the desert in Qaitam Basin, Tengger Desert, and Qubqi Desert. Their climatic variations had been characterized by the alternating appearance of cold-dry and warm-wet stages. Area-Ⅱ contains the deserts in Hexi Corridor, Badain Jaran Desert, Ulan Buh Desert, Kumtag Desert. Shanshan Desert, Taklamakan Desert, also and Qubqi Desert. They had undergone alternating periods of cold-dry and warm-dry climates. (2) The climatic changes since the Late Pleistocene in the deserts of Northern China are, in fact, the reflection of the latitudinal shifts of bio-climatic belts. In Area-Ⅰ, the bioclimatic belts had been mostly influenced by climatic variation, in unstable state. In Area-Ⅱ, the bioclimatic belts seemed relatively stable. (3) From the Late Pleistocene up to present, the stages of cold-dry/warm-wet climatic fluctuation have become shorter and shorter, namely, the frequency of the fluctuation have become higher and higher. The shifting scale of latitude has turned gradually smaller and smaller, and moved northward. This shows that the tendency of climatic variation goes to colder and drier. (4) In deserts of Northern China, especially in Area-I, the cold-warm climatic fluctuation is generally consistent with the climatic fluctuation at the glacier/interglacier ages (including New Ice Age and Little Ice Age) in Northern Hemisphere since the Late Pleistocene. The global glacier/interglacier fluctuations indicated by the variation of temperatures are the fundamental factors influencing the climatic changes in deserts of Northern China. The variances of the continentality and underlying surface in different areas may lead to some evident differences in the combination of temperature and precipitation between different periods in Area-Ⅰ and Area-Ⅱ. (5) The tendency of future precipitation up to 2050 AD may be that: with the rise of global temperature, the precipitation may increase in Area-Ⅰ, and decrease in Area-Ⅱ; if the global temperature drops, the precipitation would decrease in Area-Ⅰ, and relatively increase a little in Area-Ⅱ.