近500年来喜马拉雅山达索普冰芯中尘埃含量变化与西、南亚及北非干旱化趋势

INCREASE IN DUST CONCENTRATION IN THE DASUOPU ICE CORE FROM THE MIDDLE HIMALAYAS AND DRYING TREND IN SOUTH AND WEST ASIA AND NORTH AFRICA OVER THE LAST 500 YEARS

本文重建了近500年来喜马拉雅山中段达索普冰芯中尘埃浓度与尘埃沉积通量的变化历史,谱分析结果表明它们的变化均存在较显著的12.3年、9.8年、7.4年、6.1年和5.3年周期。该冰芯中尘埃含量与净积累量之间不存在任何相关性,说明其尘埃可能主要来源于上风方向的远源地区。基于后向轨迹法,并结合该地区附近已有的气溶胶研究结果,认为西、南亚甚至北非地区可能是该冰芯中尘埃物质的主要源区。近500年来达索普冰芯中尘埃沉积通量的增加趋势,反映了其源区干旱程度的加重趋势。

In 1997, two ice cores, 149.2m and 167.7m long, respectively, were drilled from the Dasuopu glacier （28°23′N,85°43′E） to bedrock on the col at 7200m a. s. 1. where the average annual net balance is about 1000mm water equivalent. Most of the results presented here are from 167.7m-long core （ Dasuopu ice core）. Distinct seasonal cycles,particularly in δ^18O and dust,make it possible to reconstruct an annual record for the last 500 years from the upper Dasuopu ice core. The variations in dust concentration and dust flux in the Dasuopu ice core showed significant periodicities with lengths of 12.3,9. 8,7.4,6. 1 and 5.3 years. There was no correlation between dust concentration and accumulation rate. This implied that dust source area should be located in the remote upwind regions. Based on the backward trajectories of air parcels, and along with the study on aerosols in the area near the drilling site by other investigators, it was considered that the long-range transport of dust to the drilling site in the middle Himalayas from arid regions ranging from the South and West Asia to perhaps as far as the Sahara. The increase in dust concentration and dust flux in the Dasuopu ice core over the last 500 years might reflect the drying trend in dust source regions ,especially in the last two centuries.