亚洲内陆冰芯记录的过去2000年大气硫酸根离子浓度变化研究

Ice cores provide a wealth of information on past climate and environmental changes at time scales greatly surpassing those of instrumental records. In particular, ice cores provide an ideal means to examine atmospheric transport, temperature and precipitation variability, and surface environmental changes. The proposed research will utilize ice cores from the continental interior of Asia to quantify climate and surface environmental changes over the past 2,000 years or more. Sulfate is of special interest due its climate forcing effect. Opposite to greenhouse gasses and black carbon, sulfate aerosols may cause climate cooling although uncertainties exist about the regional strength and variability. Ice cores from the western and eastern Pamir Mountains, where no previous long-term record exist, will be analyzed for sulfate concentrations in order to determine natural and anthropogenic sulfate sources and their relationships to climate and surface processes. The sulfate record will also provide a 2,000 year archive of explosive volcanism. The long-term ice core record will be validated using ground-based aerosol and climate data in order to determine the modern processes responsible for sulfate concentrations preserved in glacier ice. The long-term ice core record will result in an improved understanding of westerly circulation in relation to climate and surface environmental changes. Results will be significant at both regional and global scales, will enable the comparison of a mid-latitude record with similar records from the polar regions, and may be used for improving atmospheric chemistry and transport models.

本项目利用从亚洲内陆取得的冰芯定量研究过去2000年甚至更长时间的气候与地表环境的变化。硫酸根离子的特殊作用表现在它的气候强迫效应。尽管在区域范围内的加强程度和变化范围上还存在不确定性，但与温室气体和黑碳相反的是，硫酸根气溶胶可以引起气候的变冷效应。为了检测自然来源和人类来源的硫酸根以及他们与气候和地表过程的关系，我们将分析帕米尔山脉东西两侧冰芯（慕士塔格和Fedchenko）的硫酸根离子浓度，这一地区目前还没有该指标的长时间尺度记录。这一硫酸根记录还将提供过去2000年的火山喷发记录。基于地表的气溶胶和气候资料，冰川冰中保存的硫酸根离子的现代过程将用于验证长时间尺度的冰芯记录。长时间尺度的冰芯记录将提高我们对西风环流与气候和地表环境变化之间联系的认识。该结果对区域和全球尺度的环境变化都有重要意义，可以将对中纬度记录和极地的类似记录进行比较，同时也将有助于改进大气化学和传输模型。

冰芯可溶性离子记录是区域大气环境状况指示剂，能够反映自然来源和人类活动影响。本项目以位于青藏高原西北部的扩扩色勒冰芯和青藏高原中部的木嘎岗穹冰芯为研究对象，通过分析两根冰芯的可溶性离子记录，结合相应的冰芯稳定同位素比率、积累量、污化层等指标，对主导该地区的西风环流与气候和地表环境之间的联系进行研究。扩扩色勒冰芯Ca2+与SO42-浓度记录的过去200年来大气粉尘总体趋势是减少，尤其是1950年以来减少更为显著，中亚粉尘源区的贡献最大；NO3-浓度变化显示中亚地区从1970至2010呈现出波动上升的趋势污化层比率显示该地区沙尘天气在1900~2010年间的发生频率呈现逐渐减少的趋势。木噶岗穹冰芯冰芯可溶离子浓度在1780-1800年和1900-1950年的两个时段出现极高值，并且在1680-1730年段的波动较大，其余部分变化较为平缓。SO42−与Ca2+离子的相似性说明具有相同的粉尘及蒸发盐的来源，差异性说明SO42−离子还受到人类活动排放增加的影响。