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

为了估算和了解外海营养盐向沿海输送的机制，对两种不同类型的近岸海域进行了调查。在第一种情况下，在鹿岛沿海地区进行了实地观测，以了解黑潮对鹿岛开阔海岸营养盐分布和初级生产力的影响。观察显示，营养盐的浓度在一两个月内激增，激增的持续时间。与前期观测结果对比表明，鹿岛沿岸流系统对即将到来的黑潮有两种响应。当接近的黑潮不靠近海岸时，鹿岛海岸附近会产生一个逆时针涡旋，低盐度和低温的水从北部地区(Jyoban海岸)侵入到沿海地区。当逼近的黑潮靠近沿海地区时，高营养物质的水从近海底层向上涌出。在第二种情况下，对东京湾进行了数值试验，以了解海水入侵半封闭河口的过程。模拟结果表明，海水诱导过程涉及两种流动结构的转换：正常河口环流类型(两层)和中层入侵类型(三层)。三层结构明显，东京湾东部中层海水入侵，表层和底层沿岸水流经东京湾西部省道。这与野外观测结果吻合较好。根据数值试验结果进行的年度分析表明，海水入侵的强度和结构具有明显的季节变化，夏季入侵强度更大，海洋入侵水的核心比冬季更接近地表。

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.