New Study Maps Tidal Residual Currents in China’s Coastal Seas

KNOXVILLE, TN, September 09, 2026 /CourierPR/ -- A new comprehensive study by researchers from Xiamen University's College of Ocean and Earth Sciences and the 715th Research Institute of China State Shipbuilding Corporation Ltd. has mapped the spatial patterns and dynamics of tidal residual currents across China’s coastal seas, from the Bohai Sea to the northern South China Sea. Published in the Journal of Xiamen University (Natural Science) in May 2026, the study uses the Regional Ocean Modeling System (ROMS) to simulate barotropic tidal motion over a domain spanning 99°E to 150°E and 15°S to 41°N, at a horizontal resolution of 0.05° and with 50 vertical layers.

The research reveals distinct regional patterns of tidal residual currents. In the Bohai Sea, a large anticyclonic (clockwise) residual circulation dominates, with velocities ranging from 0.5 to 3 cm/s, except in the northern Bohai Strait, where velocities can reach up to 4 to 10 cm/s. In the Yellow Sea, several small cyclonic and anticyclonic residual circulations are observed near the coast, with a southward residual current emerging from the Bohai Strait and extending along the central Yellow Sea. In the Taiwan Strait, residual currents flow predominantly northeastward, with a strong anticyclonic circulation around the Taiwan Bank.

The study also highlights the role of tidal Stokes drift, which is comparable in magnitude to Eulerian residual currents in shallow waters but negligible in deep waters. Consequently, Lagrangian residual currents in shallow regions are directed more strongly toward the coast and are slightly faster than their Eulerian counterparts, whereas the two are nearly identical in deep waters.

Bathymetric features such as coastlines, islands, shoals, and submarine ridges play a significant role in organizing the residual-current field and generating numerous small-scale circulations. The interaction of bottom friction with velocity shear is identified as the dominant control on the overall distribution of Eulerian residual currents. The bottom-friction term associated with water-depth gradients acts mainly in localized regions, while the Coriolis term influences the background residual vorticity and several regional structures.

These findings are critical for coastal management and environmental protection, as tidal residual currents significantly influence the long-term transport and dispersion of pollutants, sediment, nutrients, and other suspended materials. For instance, the study indicates that tidal residual currents account for about 50 to 80% of the local flow between the Changjiang Estuary and the Subei Shoal and may become the dominant component in some shallow coastal areas. The results can inform coastal environmental assessment, marine engineering, channel maintenance, and the sustainable use of coastal resources.

By clarifying where tidal residual currents are strongest and which mechanisms shape them, the study provides a physical basis for assessing long-term material transport across China’s continental shelves. This research contributes to a deeper understanding of coastal dynamics, which is essential for managing and protecting China's diverse and complex coastal environments.