南海深层古环流模式的研究对于充分了解南海的深海沉积学、古海洋学、生物地球化学过程乃至全球气候变迁都有着重要的科学意义，但目前对南海深层古环流模式仍然知之甚少，阻碍了对南海深海相关过程研究的进一步深入。本项目针对这一研究薄弱环节，立足现有研究基础，通过样品采集-数据采集-数据解释-模型构建-模型应用这一技术路线，论证沉积物231Pa/230Th活度比值作为研究南海深层古环流模式的新代用指标的可行性，并利用该指标重建近15万年以来南海的深层环流模式及其变迁，揭示南海深层环流的流向、停留时间及强度等参数的演化，探讨控制南海深层环流模式及其变迁的主要机制，构建南海深层环流与生物地球化学及气候变迁相互作用的概念性耦合模型，了解南海深层环流在南海乃至全球气候变化与生物地球化学循环中的潜在作用，提高南海深层古环流的研究水平，为南海深海相关过程研究的深入开展提供更多的基础数据和科学支撑。

The paleocirculation of the deep South China Sea (SCS) played key roles on regulating the sedimentologic, paleoceanographic and biogeochemical processes of the SCS and had close connections with the global climatic change. However, little is known on the paleocirculation in the deep SCS, which has hampered the better understanding of abyssal processes in the SCS. Based on preliminary results, this proposed research will first test the hypothesis that adopting the sedimentary 231Pa/230Th activity ratio as the proxy of paleocirculation in the deep SCS following the implementary plan of sample collection and analysis, data collection and analyis, and model establishment and application. Then the paleocirculation in the deep SCS and its spatiotemporal variation over the past 150 ka will be reconstructed and investigated by examining the variations of 231Pa/230Th activity ratio in the surface and core sediments collected from the SCS. The goals of this proposed research are: (1) to unravel the variations of direction, residence time and transporting strength of the deep circulation in the SCS over the last 150 ka; (2) to distinguish the major mechanisms which regulating the paleocirculation pattern in the deep SCS; and (3) to establish the coupled conceptual model of interaction between the deep circulation and biogeochemistry in the deep SCS and global climatic change. This research will shed light on the potential role of deep circulation in the SCS on affecting the biogeochemical cycles of the SCS and global climatic change. The research outcome will also provide additional geochemical data and scientific information for the comprehensive investigation of abyssal processes in the SCS.