Variations Of Atmospheric Dust Loading Since 1950s Recorded In Ice Cores From Central Himalayas And Eastern Tien Shan

As one of the most abundant aerosols in the atmosphere, dust aerosols have recently received utmost attention due to their role in climate system, global biogeochemical cycling, hydrologic cycling, air quality, and public health. Thus, assessment of dust loading in the atmosphere is important for further understanding its impacts on climate and the environment.The arid and semi-arid regions of central Asia are a major source area for dust aerosols to the Northern Hemisphere. However, sparse meteorological stations in the central Asia and extreme climate limit our understanding of the variation of atmospheric dust loading. Fortunately, Ice cores preserve dust information including aeolian origin, windblown long distance from the continents. The vast extent of glaciers in the mountains of central Asia provides a means to measure the depositional flux of atmospheric dust over a wide geographic area. This study presents dust records of two ice cores from the East Rongbuk Glacier in the central Himalaya and the Miaoergou Glacier in the eastern Tien Shan Mountains.Based on a 39.8 m ice core drilled at the East Rongbuk Glacier (27°59’N,86°55’E, 6518 m a.s.l.), north slope of Mt. Qomolangma (Everest), central Himalaya, changes of atmospheric dust loading over the southern Tibetan Plateau recorded by insoluble particle and its possible connection with the winter Northern Hemisphere Annular Mode (NAM) were investigated. The results show that atmospheric dust loading over the southern Tibetan Plateau exhibits a significant decreasing trend during the past 50 years. This may be attributed to a decrease in wind speed over the southern Tibetan Plateau and its surrounding regions. In addition, increased precipitation in winter may also, to some degree, contribute to the decreasing trend of atmospheric dust loading. The normalized time series of the winter NAM index shows a significantly negative correlation with the mass concentration of insoluble particle implying a possible connection between the winter NAM and the atmospheric dust loading over the southern Tibetan Plateau.Based on an ice core drilled at the Miaoergou Glacier (43°03’N,94°19’E,4512 m a.s.l.) in the eastern Tien Shan, changes of atmospheric dust loading over the northwestern China recorded by insoluble particle were given. The results show that atmospheric dust loading in the northwestern China has undergone a distinct decrease since the mid-1970s. This decrease has been found to be closely associated with decreased surface winds in dust source areas. In addition, the decrease in wintertime intensity of 500 hPa horizontal wind speed, to some degree, contributed to the decrease of dust emissions in the northwestern China. The normalized time series of the winter NAM index shows a significantly negative correlation with the mass concentration of insoluble particle implying a possible connection between the winter NAM and the atmospheric dust loading over the northwestern China.