The estimation of nutrient salt flux from the outer ocean into the coastal region based on the multi-scale ocean model

基于多尺度海洋模型的外海进入沿海地区营养盐通量估算

基本信息

批准号：
13650563
负责人：
YAGI Hiroshi
金额：
$ 2.24万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

In order to estimate and understand the mechanism of nutrients flux from the outer ocean to the coastal region, two different types of coastal area were investigated. In the first case, field observations were carried out within the Kashima coastal region to understand the effect of the Kuroshio Current on the nutrient salt distribution and primary production along the Kashima open coast. The observations showed there is a surge in the concentration of nutrient salts, the duration of the surge, at one or two months. Comparison with observations made in previous periods showed that there are two kinds of response of the Kashima coastal current system to the approaching Kuroshio. When the approaching Kuroshio is not close to the coastal region, an anticlockwise gyre is induced off the Kashima coast and low-salinity and low-temperature water intrudes from the northern area (Jyoban coast) to the coastal region. When the approaching Kuroshio is close to the coastal region, high-nutrient water wells up from the offshore bottom layer. In the second case, numerical experiment were performed for Tokyo bay to understand the intrusion process of oceanic water into a semi-enclosed estuary. The simulation results showed that the oceanic water induction process involves transition between two kinds of flow structure : the normal estuary circulation type (two layers) and middle layer intrusion type (three layers). While the three layer structure is apparent, oceanic water intrudes into the middle layer of eastern part of Tokyo bay and coastal water at surface and bottom layer outflows through the western Dart of Tokyo bay. This agrees well with field observation. An annual analysis based on the numerical experiment results showed that the intensity and structure of oceanic water intrusion exhibits remarkable seasonal variation, hence intrusion in summer is stronger and the core of oceanic intrusion water is closer to the surface than that in winter.

为了估计和了解从外海到沿海地区的养分通量机制，对两种不同类型的沿海地区进行了研究。在第一个案例中，在鹿岛沿海地区进行了实地观测，以了解黑潮对鹿岛沿海营养盐分布和初级生产的影响。观察显示，营养盐浓度出现激增，激增的持续时间在一两个月左右。与以往观测结果的比较表明，鹿岛近海流系统对黑潮的逼近有两种反应。当接近的黑潮未接近沿海地区时，鹿岛沿岸会引发逆时针环流，低盐度和低温水从北部地区（常磐海岸）侵入沿海地区。当黑潮接近沿海地区时，高营养水从近海底层涌上来。第二个案例是对东京湾进行数值实验，以了解海水侵入半封闭河口的过程。模拟结果表明，海水诱导过程涉及两种流动结构之间的转换：正常河口环流型（两层）和中层入侵型（三层）。三层结构明显，海水侵入东京湾东部中层，表层和底层沿岸水通过东京湾西省流出。这与现场观察非常吻合。基于数值实验结果的年度分析表明，海水入侵的强度和结构呈现出明显的季节变化，夏季入侵较强，海水入侵水核比冬季更接近地表。