Cross-shelf variation of internal tides west of the Dongsha Plateau in the northern South China Sea

作     者：Wei Yang Ruixiang Li Yanqing Feng Huijie Xue Wei Yang;Ruixiang Li;Yanqing Feng;Huijie Xue

作者机构：State Key Laboratory of Tropical OceanographySouth China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China University of Chinese Academy of SciencesBeijing 100049China South China Sea Marine Survey CenterMinistry of Natural ResourcesGuangzhou 510300China Key Laboratory of Marine Environment Survey Technology and ApplicationMinistry of Natural ResourcesGuangzhou 510300China State Key Laboratory of Marine Environmental ScienceXiamen UniversityXiamen 361102China 

出 版 物：《Acta Oceanologica Sinica》 (海洋学报（英文版）)

年 卷 期：2023年第42卷第10期

页      面：23-35页

核心收录：

学科分类：07[理学] 0707[理学-海洋科学] 

基　　金：The Key-Area Research and Development Project of Guangdong Province under contract No.2020B1111020003 the Science and Technology Plan Projects of Guangdong Province under contract No.2021B1212050025 the Science and Technology Development Fund of the South China Sea Bureau,Ministry of Natural Resources under contract No.202205. 

主　　题：internal tide Dongsha Plateau cross-shelf variation dynamic modal decomposition coherent 

摘      要：We examine the cross-shelf variation of internal tides(ITs)west of the Dongsha Plateau in the northern South China Sea based on observations from 4 moorings deployed between August 2017 and September 2018.On the slope,the amplitude of diurnal baroclinic current ellipses are 5 times larger than that of barotropic currents.The baroclinic energy quickly dissipates during cross-shelf propagation,and barotropic currents become dominant on the shelf outside of the Zhujiang River Estuary,with the amplitude of semidiurnal barotropic current ellipses being 10 times larger than that of the baroclinic ones.Dynamic modal decomposition indicates the first baroclinic mode is dominant for both diurnal and semidiurnal ITs.The total horizontal kinetic energy(HKE)of the first three baroclinic modes shows spatiotemporal differences among the 4 moorings.On the slope,the HKE for diurnal ITs is stronger in summer and winter,but weaker in spring and autumn;for semidiurnal ITs there is a similar seasonal variation,but the HKE in winter is even stronger than that in summer.On the shallow shelf,both diurnal and semidiurnal ITs maintain a certain intensity in summer but almost disappear in winter.Further analysis shows that only the upper water column is affected by seasonal variation of stratification on the slope,variation of diurnal ITs is thus controlled by the semi-annual cycle of barotropic energy input from the Luzon Strait,while the incoherent baroclinic currents make a major contribution to the temporal variation of semidiurnal ITs.For the shelf region,the water column is well mixed in winter,and the baroclinic energy largely dissipates when ITs propagate to the shelf zone despite of a strong barotropic energy input from the Luzon Strait.