Abstract
The summertime M2 internal tide in the northern Yellow Sea is investigated with moored current meter observations and numerical current model results. The hydrodynamic model, which is implemented from the Regional Ocean Model System (ROMS) with 1 km horizontal resolution, is capable of resolving the internal tidal dynamics and the results are validated in a comparison with observations. The vertical pattern of a mode-1, semi-diurnal internal tide is clearly captured by the moored ADCP as well as in the simulation results. Spectral analysis of the current results shows that the M2 internal tide is dominant in the northern Yellow Sea. Analysis of the major M2 internal tide energetics demonstrated a complex spatial pattern. The tidal mixing front along the Korean coast and on the northern shelf provided proper conditions for the generation and propagation of the internal tides. Near the Changshan islands, the M2 internal tide is mainly generated near the local topography anomalies with relatively strong current magnitude, equal to about 30% of the barotropic component, thus modifying the local current field. These local internal tides are short-lived phenomena rapidly being dissipated along the propagation pathway, restricting their influence within a few kilometers around the islands.
Highlights
Waves in the ocean are a dominant part of the dynamics
We find that the mode-1, semi-diurnal internal tide will increase the total current in the bottom layers in the Changshan islands area where the water masses are stratified during summer
The root-mean-square error of observed and simulated currents are 0.09, 0.10, and 0.16 m/s for the presented layers. For both the observation and the simulation, the flow becomes stronger toward the bottom. This vertical structure indicates that the contribution from baroclinic components of the current can be of importance in the mooring region
Summary
Waves in the ocean are a dominant part of the dynamics. Less visible though are internal waves, existing in stratified water masses. Internal waves are a potential source for ocean mixing and can be important for material transportation. Our present work originates from an observation of currents in the water column near Changshan islands, and the results reveal a clear two-layered oscillation superposed on the strong semi-diurnal tide which characterizes the currents in the region. This internal wave will obviously modify the total current in the area. Knowledge of the currents here is useful since this is an important area for scallop aquaculture
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