Coastal circulation in the southwestern Yellow Sea in the summers of 2008 and 2009

The coastal ocean circulation off the Chinese Subei (north Jiangsu Province) coasts in the southwestern Yellow Sea in summer is studied using hydrographic data from four research cruises, moored current meter data in the Lunan (south Shandong Province) trough, and Lagrangian trajectories of satellite-tracked ARGOS surface drifters in the summers of 2008 and 2009. The hydrographic data indicate a fresh water plume extending offshore in the northeastward direction from the Sheyang River mouth and a belt of relatively cold surface temperature from the surrounding areas located offshore of the Subei coasts to the south of the plume in summer. The drifter trajectories show that the Subei coastal current, which is traditionally thought to flow southward year round, flows northward in June through July under the forcing of the southerly monsoon. A northward intrusion along the submarine valley off the Changjiang mouth is indicated by the movement of the drifters, which is persistently strong and independent of the winds. Associated with the northward flow, coastal upwelling is generated offshore of the Subei coast to the south of the Sheyang River plume, below which upwelling is generated but is shut down by the buoyancy of the fresh water at the surface. Coastal upwelling is also observed off the coast of Qingdao city in middle July through early August of 2008, which is forced by the along-shore component of the southerly and southwesterly winds. The Qingdao upwelling in summer is reported for the first time in history.