西昆仑山冰芯记录指示的塔克拉玛干沙漠南缘对流层中上部近百年大气尘埃变化趋势

Persistent Decrease of Dust Burden for about 100 Years over Middle-Upper Troposphere of the Southern Taklimakan Desert,China

钻自西昆仑山崇测冰帽海拔6 530 m的18.7 m冰芯提供了近百年间的尘埃沉积记录.冰芯记录覆盖的90 a间尘埃表现出持续下降的总趋势,大体可以分为3个阶段,即1930年之前,1930-1960年和1960年之后,尘埃浓度的降低是量级上的.几个突出的尘埃阶段出现在1900年代早期、1910年代、1920年代后期和1940年代早期,它们分别以约2.5×106、2.7×106、2.5×106和1.5×106粒.mL-1的高浓度为特征,而1970年代则表现出相对较低的浓度(5×105粒.mL-1).就年份来看,突出的高尘埃浓度出现于1906,1915,1919和1943年.根据微粒的粒径资料分析,局地输入的尘埃分量约占总值的17%,剔除后可以得到中、大尺度范围的大气尘埃沉积通量.根据后60 a资料建立的通量平均值为913μg.cm-2.a-1,大气尘埃随时间的每10 a下降速率为-124μg.cm-2,它可反映塔克拉玛干沙漠南缘对流层中上部的大气尘埃通量半个多世纪以来的变化趋势.

An ice core of 18.7 m long from Chongce Ice Cap （at an elevation of 6350 m）, West Kunlun Mts. , China, showed an overall decrease in magni tude of the total particle content for about 100 years from the beginning of the 20 century. Three phases could be identified approximately： before 1930 （going back to 1903）, 1931-1960, and 1961-1992. The conspicuous periods include the early 1900s, 1910s, late 1920s and early 1940s, of which the dust level was much higher, and the early 1970s, of which the dust level was relatively low. The dust deposit rate at the altitude was built up for the past 60 years. The mean is 1 106 μg · cm^-2 ·yr^-1 with the maximum and minimum of 3 462 and 77 μg · cm^-2 ·yr^-1 , respectively. Analyzing the volume distribution of micro-par- ticles obtained from size measurement, it is estimated that contribution of the local component is 17% of the total dust input. The rest could be taken as long-range transportation, i. e, the deposit of atmospheric dust burden in meso-large scale. Thus, the changing trend of dust flux at the troposphere altitude over the southern Taklimakan Deseft is known. The calculated deposited dust flux for the 60 years before 1992 is 913 μg · cm^-2 ·yr^-1 in average, with a decreasing rate of -120 μg · cm^-2 in a decade. This could be a representative of the regional record of the mid-upper troposphere dust burden in temporal tendency.