New Numerical Study Reveals the Hidden Power of Tidal Residual Currents in China

A groundbreaking numerical study has mapped the complex spatial patterns of tidal residual currents across China's marginal seas, from the Bohai Sea to the northern South China Sea. While these currents are often weaker than instantaneous tidal flows, they play a critical role in the long-term transport of water, nutrients, and pollutants. By utilizing the Regional Ocean Modeling System (ROMS), researchers from Xiamen University and the 715th Research Institute have successfully distinguished between Eulerian and Lagrangian residual currents, offering a more precise understanding of material movement in coastal zones.

The research reveals that bathymetric features, such as shoals and submarine ridges, significantly influence these flows. In shallow regions, tidal Stokes drift is a major factor, causing Lagrangian residual currents to differ noticeably from Eulerian measurements. The analysis confirms that bottom friction interacting with velocity shear is the primary mechanism governing these persistent flows, which can account for up to 80% of local water movement in specific areas like the Changjiang Estuary.

These findings provide essential data for coastal management, environmental protection, and marine engineering. By identifying where these currents are strongest, the study offers a robust physical framework for assessing pollutant dispersion and supporting the sustainable use of marine resources. This work serves as a vital tool for policymakers and scientists tasked with maintaining the ecological health and industrial stability of China's extensive continental shelves.