Climate Change Research Since The Middle Holocene Recorded In The Haizi Sedimentary Record Of The East Road In Urumqi

The climate change over the past nearly 100 years had important influences on the natural environment and social economy of global. And for some areas, its disadvantages far outweigh the advantages. The trend of future climate change has become the focus of our human. Therefore, global change research is becoming more and more important. The Holocene is closely related to human, so there are lots regional studies of climate and environment changes since Holocene.The arid central Asia is a famous arid area in the world, and it has a vast geographical area. However, compared to its vast area, the paleo-climate and paleo-environment of the Holocene in this region is still relatively scarce. And the geographical study on the spatial distribution is not uniform. A lake, which is Dongdaohaizi is in the arid central. Dongdaohaizi is located in the north of Gurbantunggut Desert in Junggar Basin of Tianshan mountain foot. It is a closed lake in inland arid and semiarid climatic region, where in the Neimenggu-Xinjiang Plateau. Therefore, it is more sensitive to global change, and it is better able to record the past climate and environmental change information in the Dongdaohaizi area. The Dongdaohaizi Lake situates in north Xinjiang region of China, so the climate change of Dongdaohaizi area represents the climate change of paleo-climate and paleo-environment in the north Xinjiang region. Andthe climate change research of Dongdaohaizi area will have great significance for the study of understanding the climate change pattern of the Holocene in northwest arid region, the research of global change, the protection and utilization of ecological environment in arid area, and the climate change in the future of this research area.This article took DDH profile as the object of this study. It is located in the north Shore of Dongdaohaizi Lake, which is the terminal lake of Urumqi river. Based on the OSL dating data, the susceptibility, loss on ignition, grain-size data and geochemical elements of sediments of DDH profile were analyzed comprehensively, and combined the characteristics of climate change of other parts in Xinjiang, the sequence of paleoclimatic variation since 6.25kaBP of Dongdaohai area was established. And the driving mechanism of climate change since 6.25kaBP of this region was also studied preliminary. The main results of this study as follows:(1) Based on the OSL dating data, and according to the variable characteristics of environment indexes of susceptibility, loss on ignition, grain-size data and geochemical elements, which fluctuated with the change of depth profile, the whole change sequence was divided into five stages:6.25-5.OOkaBP was a cold-arid period; 5.00-4.07kaBP was a mild and moist period, and this stage was a transition period which from a cold-arid period to a warm-humid period; 4.07-2.57kaBP was a warm-humid period but with a cooling trend; 2.57-1.07kaBP was a cold-humid period and the trend became stronger with the time; the last stage that was a cold-wet period on the whole since 1.07kaBP, while the climate was warm-arid since 0.40 kaBP. In a word, the climate of this study area went through a process of cold-arid, mild-moist, warm-humid, cold-humid and warm-arid since 6.25 kaBP.(2) According to the comprehensive comparison and analysis, we know the climate change of Dongdaohaizi area was similar to other regions of Xinjiang. And on the whole,6.25 5.00kaBP was a cold-arid period, and the climate changed to wet gradually since 5.00kaBP. While the climate changed to warm-arid since 0.40 kaBP. Meanwhile, the climate change model was complicated, and it was neither a model of cold-arid with warm-humid in monsoon region nor a pattern of cold-humid with warm-arid in the so-called west wind region.(3) The driving mechanism about climate change in Dongdaohaizi area was also discussed. In this study, the results were compared to other conclusions which related to the Xinjiang paleoclimate evolution process. From the perspective that the climate change process are similar and the regions may controlled by the similar climate system, the possible factors of climate change were analyzed simply. Moreover, the researches of climate change driving mechanism in Xinjiang areas were arranged and summarized. And the result showed that the cold-arid period of 6.25?5.OOkaBP may closely relate to the fast and violent fluctuation of solar activity. At the same time, it may be a result the combined effects of the summer monsoon and the advance of the glaciers in Western China. While the trend which becoming wet since 5.00 kaBP may affect by the westerly circulation, North Atlantic warm salt circulation and conditions of the underlying surface. And the warming and drying trend since 400 years may relate to global warming or human activities.