东海陆架与黑潮之间的双向物质输运及其对日本海和西北太平洋的影响

The Kuroshio transports not only the heat but also the dissolved material such as nutrients from the low latitude region to the middle latitude region. Along its pathway, the Kuroshio always keeps exchanging water and material with its inner shelf seas, among which the East China Sea (ECS) shelf is one of the most active places. The presence of Kuroshio and Tsushima Warm Current indicates that the material exchange between the ECS shelf and Kuroshio affects not only on the ecosystem of ECS but also on that of the Japan Sea and Northwestern Pacific Ocean. However, our understanding on the material exchange between ECS shelf and Kuroshio is limited and has no quantitative idea on how the material exchange between ECS shelf and Kuroshio affects the Japan Sea and Northwestern Pacific Ocean. With combination of historical data analysis and lower trophic ecosystem modeling, this project is designed to quantify the exchange flux of material (nutrients and biological processes related material) between the Kuroshio and the shelf region of the ECS, in the directions from the shelf sea to the Kuroshio and from the Kuroshio to the shelf sea. A special attention is given to its spatial distribution as well as seasonal and interannual variations. Meanwhile, using numerical experiments, we plan to clarify the influence of material transport in two directions (onshore and offshore) on the corresponding material concentration in the Japan Sea and Northwestern Pacific Ocean. With comparison of horizontal transport of material to its vertical transport as well as the change due to biogeochemical processes, we like to clarify the role of physical processes in controlling the variation of material concentration. The results of this project are helpful to understanding of the interaction between the Kuroshio and the coastal ocean and establish a good background for a further research on the spatial and temporal variations of nutrients and primary production in the northwestern Pacific.

黑潮在从低纬度海区向中纬度海区输送热量的同时，也输送着包括营养盐在内的各种溶解物质。在其流路上，黑潮与其内侧陆架海之间进行着多时空尺度的物质交换，其中东海陆架是交换最为活跃的区域之一。由于黑潮和对马暖流的存在，东海陆架与黑潮之间发生的物质交换不仅会影响东海，也可能对日本海和西北太平洋的生态环境产生影响。但至今对它们之间物质交换的控制过程和通量，特别是这种交换对日本海和西北太平洋的影响尚缺乏定量认识。结合历史资料与生物地球化学模式，定量估算东海陆架与黑潮之间的物质（营养盐和相关有机物）交换通量，揭示其在季节与年际尺度上的变化。通过数值试验，阐明东海陆架与黑潮之间物质交换对日本海和西北太平洋的影响。对比水平平流、垂直平流，垂直扩散以及生物化学过程所带来的物质浓度变化，揭示各种物理过程的作用。本研究将深化对黑潮与内侧海域相互作用的认识，为深入理解西北太平洋的营养盐循环与基础生产提供参考。

黑潮在从低纬度海区向中纬度海区输送热量的同时，也输送着包括营养盐在内的各种溶解物质。在其流路上，黑潮与其内侧陆架海之间进行着多时空尺度的物质交换，其中东海陆架是交换最为活跃的区域之一。这个物质交换不仅会影响东海陆架，也可能对日本海和西北太平洋的生态环境产生影响。.本项目在东海-黑潮三维物理-生态耦合模型的基础上，计算了东海陆架与黑潮区双向物质输运通量，确认台湾东北部和九州西南部以输入为主，东海黑潮中段则以输出为主。溶解无机氮（DIN）最大输送密度出现在陆架坡约140m水深，浮游植物与碎屑输送密度最大值出现在60m水深，两者均有明显的季节变化。另外，东海陆架上的浮游植物与碎屑除了被带入黑潮区以外，也会经由对马海峡向日本海输送，加上黑潮起源DIN向日本海的输送量，说明东海陆架的物质交换对日本海有很大的影响。.为了进一步厘清黑潮起源营养盐在东海陆架的作用，本项目在上述东海-黑潮三维物理-生态耦合模型中对4种外源营养盐（河流径流、大气沉降、黑潮和台湾海峡水）进行标志，评价了各自在东海陆架营养盐的输入通量、现存量以及所支持的初级生产的作用。黑潮来源DIN的输入通量和现存量都占总量的一半以上，而其它三种来源DIN的占比相当，显然黑潮是最为重要的DIN来源。对于DIP来说，黑潮依旧是最大来源，台湾海峡来源的DIP居次位，河流和大气来源的DIP贡献非常小。.另外，为了直接确认东海陆架水在黑潮区的影响范围和黑潮起源水在日本海的影响范围，将上述东海-黑潮三维模型的计算范围扩大到整个日本海和黑潮延伸体，利用保守物质示踪计算，确认了东海陆架水随黑潮经吐噶喇海峡北部流出东海，在日本以南黑潮和黑潮延伸体的上200 m水层内的分布。同时也确认了黑潮起源水经由底层向东海陆架输运，进一步从对马海峡底层进入日本海的路径。.本课题的成果对大陆架碳循环和新生产的研究有重要的参考作用，对东海的海域管理也提供了科学根据。