| Lake Barkol is located in the Barkol basin to the north of Tianshan mountains,easten Xingjiang.At an average altitude of 1570m a.s.l.Being one of arid regions in China,its climate is dry,receives the low annual precipitation(202 mm),but the evaporation is very high(1638 mm),as well as the annual and monthly in January and July mean temperature is 1.1℃,-18.6℃and 16.9℃respectively.Influencing remarkably by westerly circulation, the climate change of this area is important and significant for researching the westerly pattern and for understanding the process of the climate evolvement in monsoon and its fringe regions.Because of the small drainage area and simpler factors that control the hydrological situation of Barkol lake,combined with the fact that wide and flat bottom, even very small fluctuations in water level also can cause the large-scale advance and retreat of the shoreline.So the lake could record smaller climate fluctuations,fit to carry out the paleoclimate change research.We dug A two-meter-deep section were dug at the southwestern lake in March,2006, and then drilled out a 2.15m core in the section.The chronology measure through of the total organic carbon in the sample,among which we distilled a plant residue in 69m. Through the dating of the plant residue,we corrected the reservoir effect,which in Barkol lake was thought to be 740a associated with the factors in all aspects.Therefore we reconstructed the time series of climate variations since 8700 cal.aBP as well as tested and analyzed the climate proxy indicators,such as the carbonate content in the sediments, grain size component and magnetic susceptibility of sediment.According to the significance of these proxies,the history of the environmental changes of Barkol region in the past 8700 cal.aBP was reconstructed.8700～8000 cal.aBP can be divided into two stages.During the period of 8700～8200 cal.aBP,the climate was rather warm and dry.But the interval of 8200～8000 cal.aBP is a transitional, environment was relatively wet.Between the 8000～2200 cal.aBP,In Middle-late Holocene the climate was wet as a whole.But many inferiority arid events occurred during the periods.During the interval of 2200～4000 cal.aBP environment was very wet,though the periods oscillation acute.Two long-playing arid intervals occurred during the periods of 4000～6900 cal.aBP,namely,4300～4500 cal.aBP and around 5300 cal.aBP,the periods of 6900～7900 cal.aBP climate was wet.Since 2200 cal.aBP climate change to arid over again.Century wet intervals including this period.Compared with other records,we find that the climate variation series since 8700 cal. a BP recorded by sediments of Barkol lake is consistent with other similar studies in arid regions and the two continual arid periods in 4300～4500 cal.aBP and 5300 cal.aBP round also appeared in other records.The grain-sizes-component reflected abruptly events took place in Asian monsoon regions also.All above suggest that the rapid climate events occurred in Barkol region were ubiquitous in the arid areas,even the whole China.As far as the process of the climate environmental change recorded by the lacustrine sediments of Barkol lake is concerned,we consider that the climate change in the region is mainly impacted by the changes in solar activity.In addition,because the specific geographic conditions that it has the inter-relationship with North Atlantic Oscillation(NAO) and Thermohaline circulation through the westerlies,it is also influenced by the Asian monsoon.
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