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通过对2006~2007年长江口外缺氧区多学科历史资料和相关模拟、遥感资料的分析,深入研究了该缺氧区的生消过程和分布形态及其结构,从水文环流动力学、浮游植物繁殖(导致有机物耗氧分解)以及其他因素等角度综合系统探讨了缺氧区生消及其位置季节性变化的机制,阐释了缺氧区生消过程中多因素的协同作用,揭示了缺氧区分布形态和结构的受控机制.研究表明:冬、春季长江口外的水文环境提供了较低溶解氧(DO)含量的水体,是缺氧区形成的前期背景条件;入夏后,缺氧区逐渐向北发育成熟,受地形、有机物局地分解和黑潮次表层水涌升的影响,7~8月份长江口外缺氧区在空间上呈现出不连续的分布特征,其在内陆架具有南、北“双核”结构,并于东部外陆架亦发现一个低氧核心,各部分的缺氧程度也不相同,北部的整体上最强,南部的次之,外陆架上的最弱;夏季北部缺氧区不仅与南部缺氧区的北向分化有关,也是在局地得以发展和加剧的结果,8月达到鼎盛期,9月以后由于层化削弱很快向南退缩并消失;秋季,于南部浙江沿岸存在缺氧区,并在济州岛西南部也形成一DO低值区,但均很快消亡,同时由于所处动力环境的改变还导致外陆架DO低值区外移.跃层强度的变化及其对DO垂向输送阻隔作用的长时间累积效应对缺氧区缺氧程度具有重要影响;长江口外海域层化区域面积、各流系/水团强度和上升流、锋面、浮游植物生物量高值区的季节性变化共同制约着内陆架缺氧区的扩展及其位置的纬向(南北向)移动;黑潮次表层水等动力因素的综合作用是导致外陆架存在一个DO低值核心的原因所在;东海北部底层冷水是济州岛西南部海域DO低值区在秋季得以形成的动力学基础.长江口外特殊的海底地形以及泥质区分布对缺氧区的发育亦具有一定影响.长江口外缺氧区的生消过程、分布形态以及其结构和位置的季节变化是多种因素协同叠加综合作用的结果.
Based on the multi-disciplinary historical data, related simulation and remote sensing data of the anoxic zone outside the Yangtze River estuary from 2006 to 2007, the origin, process and distribution of the anoxic zone in the anoxic zone were studied. From the aspects of hydrological circulation dynamics, phytoplankton The mechanisms of reproduction and its seasonal changes in the anoxic zone were explored from the point of view of the multiplication of the organism (resulting in the decomposition of organic matter) and other factors. The synergistic effects of multiple factors in the anoxic zone were explained, The results showed that the hydrological environment outside the Changjiang Estuary in winter and spring provided a water body with low dissolved oxygen (DO) content, which was the precondition for the formation of anoxic zone. After entering the summer, The area gradually developed northward to the north. Influenced by topography, local decomposition of organic matter and karst sub-surface water surge, the anoxic zone outside the Changjiang Estuary spatially showed a discontinuous distribution in July-August. It has the structure of “North Core” and “North Core”, and also found a hypoxic core in the eastern continental shelf. The hypoxia level of each part is also different, the northern part is the strongest in the whole, the southern part is the second, Weak; northern summer hypoxia The area is not only related to the northward differentiation of the southern anoxic zone, but also the result of the development and aggravating in the local area. It reached its peak in August and retreated to the south and disappeared rapidly after September due to weakened stratification. In autumn, There is an anoxic zone and a low DO zone is formed in the southwestern part of Jeju Island, but both disappear rapidly. At the same time, due to the change of the dynamic environment, the low DO zone of the outer continental shelf is also displaced. The long-term cumulative effect on the vertical barrier of DO has an important effect on the anoxic degree in the anoxic zone. The stratified area, the strength and updrafts, the frontal surface, and the biomass of phytoplankton The seasonal variation of the value area constrains the extension of the anoxic region in the shelf and the latitudinal (north-south) movement of its position. The combined effect of the sub-surface water such as Kuroshio and other dynamic factors leads to the existence of a DO low core in the continental shelf The reason is that the cold water in the northern part of the East China Sea is the dynamic basis for the formation of the DO low value area in the southwestern part of the Jeju Island in the autumn.The special submarine topography and the distribution of the muddy area outside the Changjiang Estuary also have an impact on the development of the anoxic area The process of disappearance, the distribution pattern and the seasonal change of its structure and location outside the Changjiang Estuary are the result of the combined effect of many factors.