Late Holocene Climate Change Research Based On The Lake Sediments Recorded In Ebinur Lake,Xinjiang

Xinjiang province is deep inland,which belongs to Temperate continental climate zone and is almost unaffected by ocean.With so little rainfall in this area that it's ecological environment is very fragile and it is very sensitive to climate change.Ebinur Lake is located in the middle of Eurasia continent and is an inland lake in the west of Junggar basin.Because of topographical factor,Ebinur Lake is almost unaffected by water vapor from Pacific Ocean but affected by water vapor mainly from Arctic Ocean and Atlantic ocean.In this paper,we analyzed the physical and chemical properties of Ebinur Lake sediment.We reconstructed the climate during 2000cal a BP and 1600cal a BP based on its' loss on ignition(LOI),Hg and magnetic properties and discussed the driving mechanism of climate change in Ebinur Lake region.Conclusions are as follows:(1)we obtained the Paleoclimatic Significance of the three indexes based on the analysis of the physical and chemical properties of the Ebinur lake sediments and reconstructed the climate in Ebinur Lake area during 2000cal a BP and 1600cal a BP.In the Ebinur Lake area,the land and aquatic plants grew well under the condition of sufficient rainfall and humidity.Therefore,greater ignition loss of lake sediments indicated greater growth of organic plants and the more cold and humid climate condition.On the contrary,less ignition loss of lake sediments indicated less growth of organic plants and more torrid and arid climate condition.The ignition loss value indicated that it was mainly cold and humid in Ebinur Lake area during 2000cal a BP and 1700cal a BP.The precipitation reached to its' maximum in 1700cal a BP then became arid quickly.(2)The magnetic mineral deposits were mainly concentrated in the coarse sediment,coarse sediment ratio and magnetic susptibility was positively correlated.The more the content of coarse sediments,the thicker the magnetic mineral particles.(3)When the loss of ignition(LOI)increased,the mercury content increased;on the other hand,when the LOI decreased,the mercury content reduced.So the content of mercury in lake sediments to some extent could indicate information of climatic and environmental changes.(4)The comparison between LOI and magnetic susceptibility of Ebinur lake sediment shows that they have opposite Change tendency.When the ignition loss is in the high value of the section,the magnetic susceptibility is in the low value of the profile.While the LOI is ascending,the magnetic susceptibility is declining.(5)We used REDFIT of PAST3 to analyze the time series of LOI for cycle calculation and find 150a?45a?33a cycle calculation under the confidence level of 90%.The results of wavelet analysis showed that the 33A cycle was significant during the period of 1750cal a BP to1600cal a BP,and the 45A cycle was more significant in the period of 1660cal a BP to 1770cal a BP.(6)Comparison among Ebinur Lake sediment LOI,Dongge Cave Stalagmite? 18O and TSI showed that when solar radiation weakened,the Ebinur Lake area became cold and wet,while the monsoon area was cold and dry;on the contrary,when solar radiation enhanced,the Ebinur Lake area became Warm and dry,while the monsoon area was warm and moist.Thus the Ebinur Lake and Dongge cave had similar response to solar radiation.REDFIT analysis and wavelet analysis showed that there was a good correlation between the cycle of climatic change and solar cycle,which further illustrated the leading role of solar radiation on climate change.But Ebinur Lake area and Dongge cave area responsed differently to solar radiation.Dongge cave area was clearly more sensitive to solar radiation change.Comparison among Ebinur Lake sediment LOI,Iceland Hvitarvatn lake TOC and TSI showed that the temperature change in Ebinur Lake area was accordance with that of Hvitarvatn lake area.Cosidering the change of TSI,we thought that the reduced solar radiation resulted in the decreasing temperature of Hvitarvatn lake area.Solar radiation had also led to the North Atlantic water temperature reduced,thereby affecting the west wind by influencing the atmospheric temperature.As a result,the temperature in Ebinur Lake area the was changed.