南海东北部末次盛冰期以来底流演变及其与西太平洋深水洋流变化的响应机制

The South China Sea (SCS) deep water current exhibits systematic fluctuation and migration in flow path that are closely related to the current system in the Pacific Ocean. However, the key mechanisms that link these changes and lead to the fluctuations in route swing, current intensity remain unclear. In this study, we will carry out researches on the 14C age, sedimentary environment, flowing orientation, water mass properties on sediment cores retrieved from the northeastern SCS in a systematic and inter-discipline ways. Based on above analyses, we will try to unravel the sedimentary source and environmental changes of the northeastern SCS, uncovering the potential mechanisms that control the route migration and the current intensity variability, elucidating the linking mechanisms and the controlling factors between SCS deep current and Pacific Ocean. With an integration and comprehensive comparison, we will possibly reveal the characteristic of the fluctuation in flowing route and the processes of intensity variation, determine the response mechanism of SCS deep current to western Pacific Boundary Current, discuss the sources of the deep waters that enter the Luzon Strait and their influencing factors. Our study will further our understanding in the impact of the SCS deep current on the formation of deep sea sediment wave, drift sediment. It will be also prospective to construct a new sedimentological method to study deep current route and intensity, providing testing and basic material for the evolutional model of sediment wave, modeling works on Paleoceanology.

南海深水底流存在系统性波动、路径变化且与西太平洋洋流密切相关，但对底流路径摇摆移动和强度演变及其对大洋深水洋流响应机制知之甚少。项目通过对南海东北部底流路径截面系列柱状沉积物AMS14C年龄以及沉积环境、底流方向与强度、水体性质等示踪指标的系统测定和连片分析，开展末次盛冰期以来南海东北部底流路径横截面沉积物来源和沉积环境演变，底流路径摆动移动与强度演变过程及其控制因素，底流演变对太平洋洋流变化的响应机制及其影响因素等研究。运用集成和综合对比方法，揭示太平洋洋流侵入南海后底流路径摇摆变化特征和强度演变过程，确定底流演变对西太平洋边界流变化的响应机制，探讨跨越巴士海峡贯入南海的大洋水的来源变化及其影响因素。研究成果可深化认识南海底流活动对深海沉积物波、高速堆积体形成的影响作用，有望建立研究南海底流路径和强度变化的沉积学新方法，为沉积物波演化模型、古洋流的物理海洋模式提供验证数据和基础资料。

南海底层流系统性活动与西太平洋中深层水变化密切关联，洋流模态演化控制南海深海陆源沉积并对生态环境和资源形成产生影响作用，然而对末次盛冰期以来底流演变及其对大洋深水洋流响应机制知之甚少。项目对南海东北部10E203、16ZBS11柱样以及南部B9柱样沉积物的粒度组成、化学元素、磁学多指标开展精细测试和分析，利用粒度端元模型和综合对比方法，结合铁锰结核、冷水珊瑚的化学元素、Sr-Nd同位素数据，研究了末次盛冰期以来东北部陆源碎屑来源及搬运途径，揭示沉积环境阶段性、底流强度演变及其对洋流模态变化的响应和生态、资源效应。. 取得的亮点成果主要包括：（1）测定陆源碎屑粒度组成，利用开发的具自主知识产权的软件，划分南海北部动力环境分区并确定陆源碎屑输运路径，为深入研究南海海底动力环境和输运途径提供了重要基础资料；（2）通过测试和分析沉积物粒度组成、磁性参数，利用粒度端元模型方法建立沉积环境、陆源碎屑来源演变与洋流强度变化关系，提出用端元组分计算陆源贡献量新思路，促进对南海北部底流演变和南海深海过程新认识；（3）集成多指标参数确定末次盛冰期以来洋流模态由大西洋型向太平洋性切换期为15.8-14.4ka，发现南海洋盆深水来源于北大西洋深水的δ234Ui地球化学证据，揭示了南海古洋流的强弱变化受到吕宋海峡的构造隆升和海平面变化影响，支持高纬驱动的学术观点。. 项目在Quaternary Science Reviews、Continental Shelf Research、Deep Sea Research Part I等刊物发表论文12篇，发明了双体自动耦合式海洋柱状采样器钻头，开发了计算沉积物输运方式的软件。研究成果与国内外学者进行了广泛学术交流，获得同行的认同并被引用，为深化认识南海底流活动及其生态环境和资源效应提出新思路，为沉积物波演化模型、古洋流的物理海洋模式提供验证数据和基础资料。