Herein, seasonal velocity variations from the sea surface to a depth of 1000 m over the entire Kuroshio path are investigated using satellite altimetry and reanalysis datasets. The data analysis results show that velocities in the upper layer (from 0 to approximately 500 m) reach a maximum in July and a minimum in autumn (October to November) or winter (December to February) with different tendencies in each region. However, those in the lower layer (> 500 m depth) show a reversed seasonal variation—reaching a maximum in winter—especially in the continental slope area from the east of Luzon Island to the east of the Ryukyu Islands chain, which is regarded as a route of the deeper Kuroshio flow. Using a realistic general circulation model, we performed numerical experiments to clarify the role of the local wind stress as the driving force in seasonal Kuroshio velocity variations in the upper layer. These experiments revealed that seasonal Kuroshio velocity variations in the upper layer are mainly caused by the local response to wind stress upon the current itself. These numerical results cannot be explained by conventional mechanisms, such as flow–topography interactions or coastal upwelling/downwelling. On the other hand, seasonal Kuroshio velocity variations in the lower layer can be explained by the Sverdrup theory, in which barotropic responses to the wind stress curl over the area west of the Izu–Ogasawara Ridge are responsible.

在此，使用卫星测高和再分析数据集研究了整个黑潮路径上从海面到1000 m深度的季节性速度变化。数据分析结果表明，上层的速度（从0到约500 m）在7月达到最大值，在秋季（10月至11月）或冬季（12月至2月）达到最低，每个区域的趋势不同。然而，较低层（> 500 m深度）的那些则表现出反向的季节变化，在冬季达到最大值，尤其是在吕宋岛东部到琉球群岛链以东的大陆斜坡区域，这被认为是黑潮流动更深的路线。使用现实的一般流通模型，我们进行了数值实验，以阐明局部风应力作为驱动力在上层季节性黑潮速度变化中的作用。这些实验表明，上层的黑潮速度季节性变化主要是由对洋流自身的风应力的局部响应引起的。这些数值结果不能用常规机制来解释，例如流-地形相互作用或沿海上涌/下涌。另一方面，下层的黑潮速度的季节性变化可以用斯维尔德鲁普理论来解释，其中对伊豆–小gas原山脊以西地区的风应力卷曲的正压响应是负责任的。这些实验表明，上层的黑潮速度季节性变化主要是由对洋流自身的风应力的局部响应引起的。这些数值结果无法用常规机制来解释，例如流-地形相互作用或沿海上涌/下涌。另一方面，下层的黑潮速度的季节性变化可以用斯维尔德鲁普理论来解释，其中对伊豆–小gas原山脊以西地区的风应力卷曲的正压响应是负责任的。这些实验表明，上层的黑潮速度季节性变化主要是由对洋流自身的风应力的局部响应引起的。这些数值结果无法用常规机制来解释，例如流-地形相互作用或沿海上涌/下涌。另一方面，下层的黑潮速度的季节性变化可以用斯维尔德鲁普理论来解释，其中对伊豆–小gas原山脊以西地区的风应力卷曲的正压响应是负责任的。