STUDY ON DEEP CIRCULATION IN JAPAN SEA BASED ON LAGRANGIAN CURRENT MEASUREMENT.

日本海水温约为1‰，分布在日本海100米以下。由于冬季降温，西伯利亚海岸形成了合适的水，但它的运输和迁移尚不清楚。在这些日子里，日本海的海洋环境是非常重要的，部分原因是放射性废物的阻尼或油轮失事造成的溢油。直接测量电流是循环研究的必要条件。系泊式欧拉测量电流计受地形控制的影响，特别是在深层。另一方面，拉格朗日测量中中性浮子的跟踪最能有效地显示海水的输送。1995年8月，我们部署了两个ALACE（自主拉格朗日洋流探测器）浮标，在日本海300米的海面上漂流。浮子每隔10天或20天就会浮出海面，它的位置由卫星跟踪系统ARGOS固定。其中一个浮标，部署在40 43′n和136 18′e，显示出一个直径100公里的逆时针涡流，然后向东北移动了约300公里，直到1996年12月。另一个浮标部署在40 54′n和132 24′e，呈现出直径约300 km的顺时针涡旋，并向西南方向移动约100 km。300米的平均漂流速度约为5厘米/秒。这些轨迹表明，西伯利亚外的对流水在一年内到达北海道西部海岸，而水不会到达三仁海岸或山本隆起以南。ARGOS系统每天进行约10次定位，我们估计表面流约为100 cm/sec，并显示出主导潮流。

The Japan Sea Proper Water with temperature of about 1ﾟC occupies below 100m layr in the Sea of Japan. The proper Water is formed off Siberian Coast by the winter cooling, but transport and migration of it was not clarified. The marine environment of Japan Sea is of great importance in these days partly by damping of radio active wastes or by oil spill caused by wreck of an oil tanker. Direct measurements of currents are requisite for circulation study. Moored current meters, of Eulerian measurement, are affected by topographic control, especially at deep layrs. On the other hand, tracking of neutral floats, of Lagrangian measurement, is most effective to show the transport of sea water. In August 1995, we deployed two ALACE (Autonomous Lagrangian Current Explorer) floats to drift at 300 m in the Sea of Japan. The float comes to the sea surface every 10 days ot twenty days, ant its position is fixed by a satellite tracking system, ARGOS.One float, deployed at 40ﾟ 43'N and 136ﾟ 18'E,showed an anti-clockwise eddy of 100 km in deiameter, and then moved about 300 km to northeast until December 1996. The other float, deployed at 40ﾟ 54'N and 132ﾟ 24'E,showed a clockwise eddy of about 300 km in diameter, and moved about 100 km to southwest. An average drifting speed at 300 m is of about 5 cm/sec. These trajectories indicate that the convected water off Siberia reaches to off the west coats of Hokkaido within one year and that the water does not come to off the San-in coast or south of Yamoto Rise. The positioning by the ARGOS System are made about ten times a day, and we estimated surface current to be about 100 cm/sec and a dominant tidal current is shown.