南海深海地形罗斯贝波时空特征及其对深海环流变异的作用

Topographic Rossby Waves (TRWs) are low-frequency vorticity waves over sloping topography with periods of several to hundreds of days, which are bottom trapped in the presence of stratification. TRWs dominated the low-frequency velocity variance in deep seas. Previous studies show that the sink northern Pacific deep water flows southwards in the South China Sea and arises in the slope and complex topography areas due to the strong mixing of breaking internal waves, forming the cyclonic horizontal deep circulation. However, the presence of TRWs in the complex SCS topography are still unknown, and the roles of TRWs with regard to the SCS deep circulation have not been investigated. Using in-situ data, theoretical analysis and numerical simulation, this study aims to investigate the spatial-temporal characteristics of TRWs in the SCS and its dynamically exciting mechanism, and then reveals the roles of TRWs on the variation of the deep water mass characteristics and deep circulation.

地形罗斯贝波是地形β效应下产生的一种低频涡度波(周期从几天至几百天)，其底层强化特征受近底层层结的调制，主导着深海环流的低频变化。前人研究表明太平洋深层水通过吕宋“深水瀑布”在南海北部下沉，其水体在陆坡、岛屿等复杂地形区域由于内潮内波等因素混合上升，驱动了南海气旋式深海环流，对于地形罗斯贝波在南海深海环流中的作用尚无研究。本研究拟利用观测资料、理论分析以及数值模拟与诊断等方法，系统研究南海深海地形罗斯贝波的时空分布特征及其激发机制，揭示其对南海深层水团特性及深层环流变异的调制作用。

地形罗斯贝波（Topographic Rossby Wave, 或TRW）是地形β效应下产生的一种低频涡度波，其底层强化特征受底边界层层结的调制，主导着深海环流的低频变化。基于南海长期潜标观测阵列，结合数值模式模拟结果，揭示了地形罗斯贝波沿路坡分布特征，发现高频TRW自吕宋海峡往西在路坡上的能量减少，高频TRW能量增加。研究了TRW沿北部路坡的传播特征，发现地形罗斯贝波主导南海深海近底层环流变率，能解释深海近底层海流变率超过60%的方差。提出了南海上层中尺度扰动激发深海TRW的动力机制，发现南海上层中尺度涡旋的时空分布调制着深海TRW的分布特征。在复杂地形区域，TRW能量耗散能调制局地混合，进而影响深海环流。本研究提供了季节内尺度上中上层与深层能量垂向交换的一种快速通道，对于认知南海深海环流变率、理解复杂地形区域深海强混合能量来源等方面具有重要意义。