The Influence Of Topography On The Circulation In The Southwestern Yellow Sea

The currentmeter data from a bottom-mounted Acoustic Doppler Profilers (ADPs) deployed at the 30 m depth in the Lunan trough in the summer of 2008 are analyzed to study the structure and the dynamics of the circulation in the southwestern Yellow Sea in summer. The data show dominant southeastward subtidal currents during the observational period, with significant synoptical variabilities. The tidal currents at this location, on the other hand, are dominated by the M2 tide, with decreasing amplitude in deeper waters.A nested circulation model system based on the Princeton Ocean Model (POM) is set up to study the dynamics of the circulation in the southwestern Yellow Sea. The model has reproduced well the tidal and subtidal currents at the mooring site, suggesting that it can be used to study the dynamics of the circulation. The amplitude of the M2 tidal currents near the bottom of the ocean, however, has been under-estimated. The error is attributed to the erroneous vertical mixing coefficients calculated by the turbulent closure scheme in the POM model. The results of the model show that the Subei coastal currents flow northward in summer, consistent with existing studies based on satellite observations, but in contrast to the southeastward current in the center of the Lunan trough measured by the moored currentmeter. Further analysis suggests that the Subei coastal currents, the Lunan coastal currents, and the circulation in the Lunan trough are controlled by different dynamics, suggesting that the traditional view that all three currents flow coherently southward all year round is erroneous.The modeling results show that the circulation in the southwestern Yellow Sea is sensitive to the topography data used in the simulation. The simulations using the ETOPO5 elevation data and data based on local navigational chart have shown significantly different results. In contrast to the simulation based on local navigational chart showing independence of the Subei and Lunan coastal currents and the circulation in the Lunan trough, the simulation using the smoother ETOPO5 elevation data has indicated that the Subei and Lunan coastal currents and the currents in the Lunan trough vary coherently as one system. The results suggest that the Subei Bank and the Lunan trough are critical to the circulation in the southwestern Yellow Sea.