全新世以来琼东上升流形成演化及其对气候变化的响应机制

沿岸上升流在全球气候变化和生物地球化学循环中扮演了重要角色。在全球变暖日益加剧情形下，深入理解沿岸上升流的一系列变异和变化规律、影响机制和未来趋势，具有重大的理论和现实意义。琼东上升流是南海北部陆架季节性上升流系统的重要组成部分，对海南岛沿岸气候、珊瑚生态系统、海洋渔业和养殖业发展具有关键性作用。本申请拟以海南岛东侧沿岸海域柱状和表层沉积物为研究对象，针对“重建琼东上升流区海洋环境演化过程及规律，揭示琼东上升流对气候变化的响应机制”这两个关键科学问题，以“现代过程→记录(规律)重建→机制区分”为主线，开展多学科交叉与综合研究，从海洋沉积环境、海水古温度、海洋生产力和浮游植物种群结构等多个角度，构建不同时间尺度上琼东上升流演化的代表性序列，揭示气候变化对琼东上升流形成与演变的驱动机制，客观评估全球变暖下琼东上升流的变异幅度及可能影响，为该区域海洋资源可持续利用提供重要的科学依据。

Coastal upwelling is a wind-driven circulation process that replenishes the nutrients needed for biochemical activity and sustains the most biologically productive ecosystems in the ocean. Coastal upwelling zones play a disproportionally important role in the global ocean carbon cycle. In addition, coastal upwelling systems may prove more resilient to changes resulting from human activities than other ocean ecosystems because of their ability to function under extremely variable conditions. Ongoing and future modifications of coastal upwelling systems, potentially linked to global climate changes, have become an issue of increasing importance. Although there is some evidence that the vigor of coastal upwelling, at least at the decadal scale, has progressively increased as a result of anthropogenic greenhouse gas emissions, most evidence is based only on the results of the Eastern Boundary coastal upwelling systems (EBUSs). However, little is known about the behavior of Western Boundary coastal upwelling systems (WBUSs) in response to the modern climate changes. .Under the southwesterly monsoon forcing, summer upwellings in the northern South China Sea (NSCS) are seasonal common phenomenon associated with basin-scale processes. The NSCS summer upwelling systems, as one of major WBUSs, together with river plumes significantly influence the biogeochemical processes and sea-air CO2 fluxes of NSCS. Among which Qiongdong Upwelling (QDU), off the east coast of Hainan Island, plays an important role in the regional climate, coastal ecosystems, as well as marine fishery and farming, and thus has received considerable attention during the past decades. Most of previous studies about QDU are by far based on short instrumental records and numerical simulation, aiming to decipher its structure and spatio-temporal variation. Longer temporal records are urgently needed to provide good constraints on the timing and magnitude of QDU change and therefore an assessment of the climate sensitivity of the QDU. This is especially important for the already stressed upwelling ecosystem in this region due to overfishing, pollution, and growing demand for seafood. In this proposal, an integrated study of the evolution of QDU during the Holocene will be conducted. We will reconstruct the multi-dimension records at different timescales (millennial vs. centennial) using multidisciplinary proxies (sedimentology, geochemistry, ecology, etc.): (1) changes in marine sedimentary environment; (2) changes in sea surface temperature (SST); (3) changes in marine productivity and phytoplankton community structure. These high temporal resolution sedimentary records can provide critical clues on the initiation, evolution and impact of QDU and its forcing mechanism. This will help us to decipher how will the QDU’s respond to climate and global change, which is most importantly for society.