Abstract
In this study, strong internal tides were observed on the continental slope northeast of Taiwan Island. Owing to the lack of long-term observations, these tides’ intraseasonal variability and the impact of the Kuroshio Current remain unclear. This study aimed to fill in the gaps using one-year continuous mooring observations, satellite data and analysis data. The horizontal kinetic energy (HKE) of semidiurnal internal tides showed that there was conspicuous energy from 100 days to 200 days, which was mainly attributed to the cross-term of HKE. The impact of the Kuroshio Current and mesoscale eddies on the HKEs were assessed: Cyclonic (anticyclonic) mesoscale eddies propagated from the open ocean, weakened (strengthened) the Kuroshio and shifted the Kuroshio onshore (offshore) northeast of Taiwan Island. The weakened (strengthened) Kuroshio increased (decreased) the shoreward velocity at the mooring site, and the onshore (offshore) Kuroshio migration increased (decreased) the northeastward velocity and enhanced (weakened) the HKEs of internal tides by modulating the tidal energy horizontal propagation. The weakened (strengthened) Kuroshio also resulted in gentler (steeper) isopycnals across the slope and enhanced (weakened) the HKEs of internal tides by influencing the interaction between ocean stratification and bottom topography.
Highlights
Introduction published maps and institutional affilInternal tides, which are generated in stratified waters through the interaction of barotropic tides and varying bathymetry, such as shelf breaks, ridges, sills and submarine canyons [1,2,3], are widely distributed in oceans
A rotary spectral analysis was performed on the current velocity
This finding suggested that the semidiurnal internal tide was much stronger than the diurnal tide
Summary
Internal tides, which are generated in stratified waters through the interaction of barotropic tides and varying bathymetry, such as shelf breaks, ridges, sills and submarine canyons [1,2,3], are widely distributed in oceans. The vertical structure of internal tides is very complex, and current shear tends to induce intense instability, turbulence and diapycnal mixing [4,5,6]. Internal tides play an important role in maintaining ocean stratification and meridional overturning circulation, as well as energy redistribution [7,8]. Internal tides pose hazards for acoustic transmission and underwater navigation [9]. Further study of internal tides, including of their generation, propagation and dissipation, can improve numerical simulations and understanding of the dynamic ocean environment. The observation of internal tides can be traced back to the early nineteenth century, and the linear theoretical model for internal tide generation has been in use since it was iations
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