Studies on oceanic eddies in the Northwestern Subarctic Pacific

1993年至1997年夏季在亚北极太平洋西北部千岛群岛以南地区进行的水文调查表明，在Bussol海峡以南几乎相同的位置存在反气旋涡流，但其大小和强度随年份而变化。每个涡旋都有一个低温、低盐度和低位涡核，表明受鄂霍次克海水的强烈影响。卫星数据分析发现了两个形成过程和年变化。一种情况是，涡旋在布索尔海峡以南当地形成，1993年观测到，随着鄂霍次克海水的供应，涡旋从夏季到秋季加剧。在另一种情况下，从1995年夏到秋，黑潮暖核环在布索尔海峡附近被捕获，并随着鄂霍次克海水的供应而扩大。在冬季，漩涡会随着腐烂物向东北方向移动。1992-涡旋冬季先向东北方向移动，后向北移动，最终被东堪察加海流吸收。讨论了布索尔涡旋的东北运动和形成机制。沿千岛-堪察加海沟深东北流的伪β效应可能是东北移动的原因。由于鄂霍次克海和亚北极西部环流（WSAG）之间的位涡差限制了南千岛群岛沿岸大潮水的体积输送，当鄂霍次克海流出量超过临界输送量时，漩涡就会产生并加剧。观测到的涡旋演变的年变化可以用与WASG年变化相关的临界输运变化来解释。

Summer hydrographic surveys from 1993 to 1997 in the area south of Kuril Islands in the northwestern Subarctic Pacific showed theexistence of anticyclonic eddies south of the Bussol' Strait at almost the same location but with variable sizes and intensities depending on the year. Every eddy had a cold, low-salinity and low-potential vorticity core, suggesting a strong influence from the Okhotsk Sea water. Two formation processes and annual variations were found with satellite data analyses. One is the case where eddies are locally formed south of the Bussol' Strait and intensified from summer to fall with the supply of Okhotsk Sea water as observed in 1993. In the other case, Kuroshio warm-core rings that had translated north-eastward are arrested near the Bussol' Strait and amplified with the supply of Okhotsk Sea water as seen from summer to autumn in 1995. In winter, eddies tend to move north-eastward with decay. 1992-eddy moved northeastward then northward in winter, and was eventually absorbed into the East Kamchatska Current. Mechanisms of the northeastward movements and the formations of the Bussol' eddies were discussed. Pseudo-beta effect due to deep north-eastward currents along the Kuril-Kamchatka Trench could be responsible for the northeastward movement. Since the volume transport of the coastal Oyashio water along the southern Kuril Islands is constrained by the potential vorticity difference between the Okhotsk Sea and the western Subarctic Gyre (WSAG), eddies could be generated and intensified when a outflow rate from the Okhotsk Sea exceeds the critical transport. The observed annual variations of the eddy evolutions might be explained by the critical transport variation associated with an annual change of the WASG.