The study on the monitoring of oceanic condition in the East China Sea

本研究的目的是利用生物地球化学示踪剂，估算在一个月左右的大调查区域内获得的海洋数据中的短周期和小尺度变化分量，阐明水体的现状体系和分布机制。主要研究结果如下：(1)在110 m深度的陆架上进行了17次55小时的循环测量，在3个测点之间间隔约15 km，得到了含生物地球化学示踪剂（营养物等）在内的水性质三维分布的潮汐周期变化。(2)通过在大陆架断裂附近穿越黑潮锋的短线10天内多次重复的测量，发现低盐度水向黑潮水中层俯冲的时间尺度仅为几天。(3)通过在黑潮或陆架地区同一站点间隔5 ~ 10 d的测量，发现黑潮的变化伴随着水体性质的较大变化。(1)通过在大陆架和黑潮地区进行的4次精确站距的广域测量，获得了详细的水体性质和水流的三维分布。(2)我们找到了非保守物质，如颗粒有机物（碳、氮）、叶绿素、营养物质、氧，以及荧光细胞仪分辨出的三个微浮游生物群落的每一个数量，作为水体团块识别和跟踪其运动的指标。(3)盐度和溶解氧略低于黑潮水的水团占据了相当大的外大陆架面积。

The objectives of our research program are to estimate the shot-periods and small-scale variation components in the oceanographic data obtained during about one-month long cruise in wide survey area, and to elucidate the current system and distribution mechanism of water mass by using the biogeoche-mical tracers. The major results are as follows.1. Short-periods and small-spatial scale variations (1)By the 17 cyclic surveys for 55 hours running around 3 points ca 15 km apart over the continental shelf of 110 m depth, we have obtained the tidal period variations of 3-D distributions of water properties including biogeochemical tracers (nutrients etc.). (2)By the surveys repeated several times during about 10 days along short lines crossing the Kuroshio front near the continental shelf break, we have found the time scale of low salinity water subduction into the middle layer of Kuroshio Water to be only a few days. (3)By the surveys 5 to 10 days apart at same stations in the Kuroshio or continental shelf region, we have found the large variation of water properties to be accompanied with the variation of Kuroshio.2.Discrimination and tracking of water masses (1)By the four wide area surveys with fine station spacing over the continental shelf and the Kuroshio regions, we have obtained the detailed 3-D distributions of water properties and currents. (2)We have found the non-conservative materials such as particulate organic matter (carbon and nitrogen), chlorophyll, nutrients, and oxygen, and each amount of three communities of picoplankton discriminated by fluocytometer to be utilized in the discrimination of water masses and tracking their movements as the indicators. (3)We have found that the water mass of which salinity and dissolved oxygen are slightly lower than the Kuroshio Water, occupies the rather wide area over the outer continental shelf.