Late Holocene Aeolian Activities Recorded By Lake Sediments From Gahai Lake And Bosten Lake Of Northwestern China

Dust weather and its aerosols not only affect human production and life,but also have important implications for the global climate system.The inland desert region of western China is one of the regions with the strongest aeolian activities of the world.But the history of high-resolution aeolian activities in continuous stratigraphic and reliable dating since the late Holocene is relatively lacking.This paper takes Gahai Lake in the northeast margin of Tibetan Plateau and Bosten Lake in the northern margin of the Tarim Basin as the research object of study to reconstruct the aeolian activity history of the area.In this paper,the sedimentary record of Gahai Lake is mainly studied,supplied by the record of Bosten Lake.The two lakes have their own characteristics,Gahai is an inland closed lake supplied by groundwater and rainwater,with continuous sedimentation for the past few thousand years.On the lake area has with precipitation,low vegetation coverage,sand dunes distribution on the lakeside and high frequency of strong wind by the impact of seasonal cold air in northern China.The Bosten Lake is located in the Yanqi Basin,an arid area with samll precipitation.These two lakes and their sediment cores are surrounded by sand dunes and sandy lands,therefore both lakes are ideal sites for the study of aeolian activities.To reconstruct the historical sequence of aeolian activities in Gahai lake area,the grain size analysis was conducted to the samples from GH15B core,sandbank,sand dune and eaolian dust trapped by ice column,supplemented by evidence of particle micromorphology.Two drill cores with the length of 210 cm?GH15B?and 40 cm?GH17B?respectively were acquired and reliable time series were established by using AMS ¹⁴C,²¹⁰Pb and ¹³⁷Cs dating.Grain size-standard deviation model and end-member analysis model were applied to extract particle size components which sensitive to environmental changes.Component 3?>63.24 m?and component?EM2+EM3?were selected to reconstruct the history of aeolian activity since nearly3750 cal yr BP.The results show that the sequence of aeolian activity history can be divided into four stages:3750²500 cal yr BP stage has a low aeolian activity frequency occurrence;2500⁷00 cal yr BP stage aeolian activity's intensity and frequency were significantly increased compared with the previous stage;700²50cal yr BP stage is a perriod with the highest frequency and intensity of aeolian activity throughout the late Holocene.After 250 cal yr BP,the intensity of aeolian activity decreased rapidly.The record indicates that in the past 1000 years,there are four main stages with high frequency and intensity of aeolian activities appeared:1270¹305AD?1340¹440 AD?1490¹510 AD and 1650¹760 AD.In addition,the Bosten Lake reconstruction results show that the aeolian activity is the strongest in the two periods of 280⁴10 AD and 1320¹800 AD,410¹320 AD is the weakest,while the overall performance of the two periods since 70²80 AD and 1800 AD is relatively weak.Based on the reconstruction of aeolian activities,the occurrence mechanism and regularity of eolian activities are discussed.The main conclusions are as follows:?1?The history of aeolian activities recorded in the sediments of Gahai Lake and Bosten Lake shows that the intensity of sandstorm activity in the study area is mainly related to temperature on the scale of 100 years and 10 years,and the enhancement of Siberian high caused by low temperature increases the surface wind speed.?2?The strong aeolian activity recorded by sediments in the Bohai Lake is consistent with the weak summer monsoon recorded by the oxygen isotope of the stalagmites,indicating that the low temperature restrains the intensity of the summer monsoon and the decrease of precipitation may further leads to strong aeolian activity in the monsoon margin.?3?Temperature reconstruction results show that the temperature of the Tibet Plateau began to warm up at 1735 AD,and the aeolian activity recorded in the sediments of the Gahai Lake showed a simultaneous weakening trend in the mid-18th century,indicating that the weakening of plateau aeolian activity may be closely related to plateau warming.Therefore,under the background of global warming in the future,regional aeolian activity may be weakened.?4?By comparison,on a long-term scale,it was found that dust activity increased in northern China,eastern China and the Tibet plateau in the late holocene,while the dust records in Xinjiang and Central Asia did not show an increase,which may be related to the wetting of the westerly region.There may be a positive feedback mechanism between long-term enhanced aeolian activity and sustained global temperature decline.