泸沽湖沉积记录的末次冰期以来区域降尘变化及其与降水间的关系研究

The interrelation between aeolian dust and precipitation have been key scientific issues in recent Indian Summer Monsoon (ISM) studies. However, there are few studies refer to the long time scale change of aeolian dust in southwest China which is influenced by ISM. Therefore, this project aims to fill this research gap. High-resolution grain size, elements, and minerals analysis of an AMS14C dated sediment core retrieved from Lugu Lake provides a detailed history of aeolian dust and precipitation changes since last Glaciation. Trace elements and Hf-Nd-Sr isotope measurements are performed to trace the sources and the provenance of long-range transported of Southwest China dust. The grain size data of core sediments of Lugu Lake are unmixed with a hierarchical clustering endmember modeling to extract the aeolian dust component. We also analyze the grain size, elements, and minerals of the watershed surface sediments and lake surface sediment from Lugu Lake. The surface sediments study indicates that Sr/Rb ratio of Lugu Lake core sediments can be used as a proxy of regional precipitation. So, we can reconstruct the sequences of aeolian dust and precipitation in southwest China since the last Glaciation. Mathematical statistics and wavelet analysis are performed to determine the interrelation between aeolian dust and precipitation at different time scales. This project will provide a series of high-resolution paleoclimate records for understanding the evolution of ISM since the last Glaciation. The results of this project will have important implications for understandings aeolian dust and rainfall responses to global changes. They will further provide key and basic data for the understanding of the regional climate changes, predicting future and long-term climate change.

大气降尘与降水关系研究是近年来印度夏季风研究的重要领域之一。然而目前我国受印度夏季风影响的西南地区长时间尺度降尘研究却严重不足。本申请以具有末次冰期以来高精度定年的泸沽湖钻孔沉积物为主要研究对象，对钻孔沉积物、大气降尘、湖泊表层沉积和流域现代样品进行粒度、元素(同位素)和矿物测试。首先明确自然背景下西南地区大气降尘的特征及来源，之后，利用端元分析方法提取泸沽湖沉积物粒度中的降尘组分，并结合表层样品粒度和元素现代过程研究结果，重建末次冰期以来西南地区大气粉尘和降水变化序列，从而探讨末次冰期以来不同时间尺度和气候背景下，我国西南地区大气降尘的变化特征和规律，并厘清其与大气环流和水汽输送路径间的耦合关系。研究结果有助于理解区域降尘和降水对全球变化的响应，为认识过去气候变化的区域差异及预测未来气候变化提供基础数据。

粉尘循环是全球气候系统变化研究的重要内容，湖泊沉积是重建过去大气粉尘变化的良好地质载体。然而目前我国受印度夏季风影响的云南地区长时间尺度降尘研究却严重不足。项目以具有高精度定年的泸沽湖末次冰期以来具有高精度定年的泸沽湖钻孔沉积物为主要研究对象，对钻孔沉积物、大气降尘、湖泊表层沉积和流域现代样品进行粒度、元素（同位素）和矿物测试。首先明确自然背景下云南地区大气降尘的特征及来源，之后，利用端元分析方法提取泸沽湖沉积物粒度中的降尘组分和径流动力组分，并结合表层样品粒度和元素现代过程研究结果，重建末次冰期3万年以来云南地区大气粉尘变化序列，从而探讨3万年以来不同时间尺度和气候背景下，特别是末次冰期最盛期和全新世云南地区大气粉尘的变化特征、幅度和规律，并厘清其与大气环流和水汽输送路径间的耦合关系。研究发现32 ka以来泸沽湖沉积物主要由流域径流输入的砂、粗砂等物质和源自印度北部和德干高原的远源降尘组分构成，二者分别占到总物质量的31.2%和32.8%。HYSPLIT模型分析发现，远源降尘组分在干季时以西风南支携带的印度北部物质为主，雨季时以南亚夏季风携带的德干高原物质为主。泸沽湖沉积物降尘组分含量的高低主要受控于其源区（即印度北部和德干高原）气候与环境的变化，32 ka以来降尘组分含量不断升高（Bølling-Allerød暖期略有下降），至9 ka开始骤然降低，整个“中全新世适宜期”降尘组分均很低，自2 ka开始快速升高直至当代。研究结果有助于理解区域降尘对全球变化的响应，为认识过去气候变化的区域差异及预测未来气候变化提供基础数据。