Tidal energetics in the eddying South China Sea from a high-resolution numerical simulation

Understanding tidal energetics is crucial for comprehending complex oceanic processes in the South China Sea (SCS). Tidal energy budget in different parts of the world’s oceans has been widely estimated, but the dissipation pathways of tidal energy in the eddying ocean remain elusive. Based on a well-validated high-resolution numerical simulation, this study provides an updated estimate of tidal energy budget in the SCS with the modulation of realistic background currents and stratification. It reveals that ∼19.72% of barotropic tidal energy input in the Luzon Strait (LS) is converted to baroclinic tides, ∼75.66% of which is transmitted out of the LS and the other ∼24.34% is dissipated locally. Additionally, ∼61.20% of barotropic tidal energy is transmitted into the SCS, and the other ∼19.07% is dissipated locally. Analysis of barotropic tidal energy budget highlights significant work rate of K₁ tide-generating force in the SCS, whereas analysis of baroclinic tidal energy budget reveals the impacts of background fields on energy conversion from barotropic to baroclinic tides and energy dissipation of baroclinic tides. The seasonal variability of tidal dynamics and energetics further highlights the modulations by background fields. An exponential decay of baroclinic tidal energy flux with the distance from the generation site is revealed, and the decay scales for K₁ (northwestward and southwestward beam of M₂) baroclinic tide are estimated as 404 (195 and 127) km. A simple scaling of baroclinic tidal energy flux in the SCS, which may be used to characterize tidal mixing in large-scale ocean and climate models, is thus devised.