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Mechanism of clockwise circulations in the southern Sea of Okhotsk

鄂霍次克海南部顺时针环流机制

基本信息

批准号：
17540406
负责人：
MITSUDERA H.
金额：
$ 2.24万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540406/
关键词：
The Sea of Okhotsk The Kuril Islands tidal mixing North Pacific Intermediate Water clockwise circulation thermohaline circulation East Sakhalin Current Soya Warm Current 中規模渦多重平衡

项目摘要

Clockwise circulations are dominant in the Kuril Basin, the southern portion of the Sea of Okhotsk. Correspondingly, potential vorticity (PV) in the intermediate layer is low in this region. In this project, formation processes of the clockwise circulation were investigated.First, effects of localized mixing around the Kuril Islands were considered. A two-layer model with a submarine ridge was used, and mixing is parameterized as diapycnal vertical velocity over the ridge topography. When the mixing commences, the interface deepens over the ridge locally. For weak mixing cases, the depth of the interface corresponds well to a linear beta-plume solution. If the mixing becomes stronger, low PV water forms first over the ridge. Then, the low PV water is carried westward by eddies and waves, letting low PV water occupy the entire region west of the ridge. It is noted that the lower layer flow around the ridge gives significant influences on the circulation through modifying characteristics … More of the upper-layer wave. In particular, if the characteristics have closed contours, then PV input due to vertical velocity is hardly radiated from the topographic region until the interface becomes so deep that baroclinic instability can take place. Bimodal states in the clockwise circulation are found.Second, a high resolution Okhotsk Sea Model, with a 1/12 degree horizontal resolution, was used to investigate wind-driven circulation. The clockwise circulation in the Kuril Basin is formed as a recirculation gyre associated with an eastward jet that extends from the East Sakhalin Current. Both the numerical results and the altimeter data from satellites indicate that this circulation has an annual signal corresponding to the annual variations in wind-stress.From these experiments, it has been found that the clockwise circulation in the Sea of Okhotsk has rich structures incorporating both wind-driven and thernmohaline components. An analytical model that investigates impacts on the intermediate layer circulation was also constructed. Further, analysis of data from the intensive CTD survey across the Bussol' Strait were carried out to estimate the vertical mixing strength along the Kuril Islands. Less

在鄂霍次克海南部的千岛盆地，顺时针环流占主导地位。相应的，该区域中层的位涡量（PV）较低。在这个项目中，研究了顺时针环流的形成过程。首先，考虑了千岛群岛周围局部混合的影响。采用带海底脊的两层模型，混合参数化为沿海底脊地形的垂直速度。当混合开始时，界面在脊上局部加深。在弱混合情况下，界面深度与线性β -羽流溶液很好地对应。如果混合变得更强，低PV水首先在脊上形成。然后，低PV水被涡旋和波浪向西携带，使低PV水占据了脊西的整个区域。注意到低空脊周围的低层气流通过改变上层波的特征对环流有显著的影响。特别是，如果特征具有闭合轮廓，那么由于垂直速度的PV输入几乎不会从地形区域辐射出来，直到界面变得非常深，从而可能发生斜压不稳定。在顺时针循环中发现双峰态。其次，利用水平分辨率为1/12度的鄂霍次克海高分辨率模式研究风驱动环流。千岛盆地的顺时针环流形成于一个与东库页流延伸的东喷流相关的再环流环流。数值结果和卫星高度计资料均表明，该环流具有与风应力年变化相对应的年信号。从这些实验中发现，鄂霍次克海的顺时针环流具有丰富的风驱动和热盐成分的结构。建立了对中层环流影响的分析模型。此外，对Bussol海峡密集CTD调查的数据进行了分析，以估计千岛群岛沿岸的垂直混合强度。少