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Studies on oceanic eddies in the Northwestern Subarctic Pacific

西北亚北极太平洋海洋涡流研究

基本信息

批准号：
09640515
负责人：
YASUDA Ichiro
金额：
$ 1.15万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

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.

1993 ~ 1997年夏季在北太平洋千岛群岛以南海域进行的水文调查表明，在布索尔海峡以南几乎相同的位置存在反气旋涡旋，但其大小和强度随年份而变化。每个涡旋都有一个冷的、低盐度和低位涡的核心，表明受到鄂霍次克海水的强烈影响。卫星资料分析发现，该地区有两个形成过程和年际变化。一种是1993年观测到的在布索尔海峡南部局部形成的涡旋，并随着鄂霍次克海水的供应而从夏季到秋季增强。在另一种情况下，黑潮暖心环，已经向东北方向移动，被逮捕附近的布索尔海峡和放大与鄂霍次克海水的供应，从1995年夏季到秋季。在冬季，涡旋倾向于向东北方向移动并逐渐减弱。1992-冬季涡旋先向东北移动，然后向北移动，最后被东堪察加海流吸收。讨论了布索尔涡旋向东北移动的机制和形成过程。沿千岛-堪察加海沟沿着的深北东向海流产生的伪β效应可能是造成该海流向东北方向运动的原因。由于北千岛群岛南部沿岸Oyashio水沿着的体积输送受到鄂霍次克海和西亚北极环流（WSAG）之间的位涡差的限制，当鄂霍次克海的流出速率超过临界输送时，涡旋可能会产生并加强。观测到的涡动演变的年变化可以用与WASG年变化相关的临界输送变化来解释。