青藏高原冰芯Hf-Nd-Sr同位素重建风尘物源时空变化及其影响机理研究

Asian (wind-blown) dust has important climatic and environmental impacts both regionally in central Asia and over the entire Northern Hemisphere. The Tibetan Plateau environment was also significantly influenced by Asian dust, which has been revealed from previous ice core studies. Asian dust transport, deposition and its climatic effects are important scientific issues in current study on the Tibetan Plateau. Besides, snow/ice are globally regarded as excellent archives for documenting the modern and past changes in eolian dust deposition. The Tibetan Plateau, known as the "Third Pole", is remote and isolated, and presumed to be a pristine region characterized by its extremely high altitude and harsh climatic conditions. Therefore, ice cores retrieved from the high altitude glaciers are ideal for historical reconstruction of eolian dust source variation over the Tibetan Plateau. However, until present little studies have been carried out on the provenance of eolian dust deposition in historical variation over the Tibetan Plateau, which need to be carried out urgently to evaluate the essential climatic and environmental information during past hundreds years. The geochemical fingerprint of Hf-Nd-Sr isotope has been employed as a powerful method for distinguishing dust sources. Therefore, in this research project, several deep ice cores were drilled from different climatic areas to reconstruct the variation of eolian dust deposition during the past several hundred years over the Tibetan Plateau. We plan to comprehensively interpret the temporal and spatial differences in long-term variation of eolian dust provenances through contrastive and integrated analyses of several ice core Hf-Nd-Sr isotopic records, and explore the influence mechanisms behind these differences; and quantify the relative contribution of different dust sources to dust deposition on the plateau, thus to infer the historical interaction of different climatic systems (e.g., the Westerlies and the India Summer Monsoon). This research will not only enhance our understanding of eolian dust related Hf-Nd-Sr isotopes biogeochemical cycling in the "Third pole" region, but also provide beneficial reference and new basis in forecasting the future eolian dust and climatic-environmental change of the Tibetan Plateau.

雪冰中的粉尘能够敏感地记录大气环境信息，在反映大气粉尘变化方面具有独特的优势，风尘沉积相关研究也是当前“第三极”冰川与气候环境变化研究的热点。Hf-Nd-Sr同位素证据是一种强有力的区分粉尘物源的手段。本研究拟结合青藏高原数支深孔冰芯的Hf-Nd-Sr同位素记录，开展冰芯长序列示踪同位素的风尘物源时空差异及其影响机理的研究。通过本项目的开展，获得青藏高原典型气候区高分辨率的冰芯Hf-Nd-Sr同位素组成和模态的时空变化；结合相关冰芯记录的环境参数和指标集成分析，揭示青藏高原面上过去数百年乃至千年尺度的风尘物源及其传输路径演化的历史过程，反演西风和季风系统之间的相互作用。项目的实施无疑会揭示出历史时期青藏高原面上不同区域风尘来源的谜团和演化规律，将为亚洲粉尘和“第三极”气候环境演化研究做出新贡献，为预估青藏高原未来气候环境变化提供重要依据。

亚洲粉尘对大气系统、生物地球化学循环和人类健康有重要影响。雪冰中的粉尘能够敏感地记录大气环境信息，在反映大气粉尘变化方面具有独特的优势，风尘沉积相关研究也是当前“第三极”冰川与气候环境变化研究的热点。Hf-Nd-Sr同位素证据是一种强有力的区分粉尘物源的手段。目前已经基本完成本项目研究目标，揭示了青藏高原典型气候区高分辨率和时空变化序列的雪冰Hf-Nd-Sr 同位素沉降现代过程记录及风尘物源解析，获得亚洲风尘高海拔传输的物源和传输路径图谱；全面深入认识青藏高原面上风尘物源演化的过程、时空差异并阐明其影响机理。为青藏高原地区风尘和气候环境演化研究提供新的证据，为评估和预估该区气候环境演变提供新的依据；同时，基于项目获取了青藏高原一批宝贵的雪冰Hf-Nd-Sr 同位素与粉尘变化的观测分析资料。.本项目通过引入Hf-Nd同位素等新方法, 揭示青藏高原雪冰中粉尘气溶胶传输的来源和时空变化，评估中亚粉尘高海拔大范围传输循环及其对冰冻圈环境和雪冰吸光性增强的影响。沉降在冰川和积雪表面的粉尘气溶胶能够降低雪冰反照率加速冰川消融， 并为冰川微生物生长提供所必需的微量元素如铁和钙等。基于本项目研究了青藏高原及周边不同区域代表性冰川和积雪区域冰尘中粉尘气溶胶传输沉降的含量和粒度分布及其同位素指纹证据(Hf, Nd, Sr, Pb)的来源示踪；评估了青藏高原及周边冰川区的雪冰粉尘的沉降通量和浓度、时空分布，揭示青藏高原及周边冰川区和中亚内陆的雪冰中粉尘气溶胶含量主要受到距离源区远近和源区强弱、大气环流的共同影响。系统分析了青藏高原不同区域的表土粉尘Hf-Nd-Sr同位素组成和分布，是对全球粉尘循环和源区判断的重要补充和完善。青藏高原冰川远距离粉尘源的显著空间差异主要是由春季和夏季大尺度大气环流相互作用(如东亚季风、蒙古高压和西风带)引起的。此外，青藏高原冰芯中粉尘Hf-Nd-Sr同位素显示了中亚粉尘源区在千年尺度上的同位素踪迹变化，传输路径变化和影响要素，揭示出主要受到该区域大气环流相互作用的影响。