Ice core record in an Asian glacier of 6530m a.s.l.: Overall declination of atmospheric dust flux for past 60 a

摘要

Based on continuous measurement along a 18.7m long ice core drilled from an Asian glacier, with elevation of 6350m a.s.l., dust concentration record for past more than 90 years, going back to the beginning of the 20 century, was studied. A representative Asian dust flux at the middle-high tropospheric altitude was built up for the last 60 years. Overall variation of dust content shows a decreasing trend. Three levels could be identified in general: before 1930 (back to 1903), 1931-1960, and 1961-1992. The conspicuous periods are: the earlyl900s, 1910s, late 1920s and early 1940s marked by much higher dust level and the early 1970s showing a relatively low dust level. The mean total mineral dust flux for the entire period is 1106 μg cm~(-2) yr~(-1) with the maximum and minimum of 3462 and 77 μg cm~(-2) yr~(-1) respectively. According to volume distribution of particle size measurement, it was known that local component was estimated to 17% of the total dust input, while that over 80% comes from "long range" transportation. The prevailing atmospheric circulation pattern for major dust season suggests that the gigantic Taklimakan Desert south of the sampled glacier serves, in high probability, as the principal source area. The similar trend variation for compatible time span also supports the possible relation of sink to source.