Winter Counter‐Wind Transport in the Inner Southwestern Yellow Sea. Issue 1 (18th January 2018)

• Record Type: Journal Article
• Authors: Wu, Hui; Gu, Jinghua; Zhu, Ping
• Is Part Of: Journal of geophysical research. Volume 123:Issue 1(2018)
• Page Start: 411
• Page End: 436
• Publication Date: 2018-01-18
• Subjects: coastal current -- tidal stress -- upshelf -- southwestern Yellow Sea; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2017JC013403
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Coastal currents generally flow downshelf with land on the right side (Northern Hemisphere) under the geostrophic balance, and are often strengthened by downwelling‐favorable winds. However, the recent mooring observation in the inner southwestern Yellow Sea showed that coastal transport direction can be substantially changed by tidal forcing. In the survey, the tidal‐averaged transports at two out of three sites remained northward (i.e., in the upshelf direction) and opposite the downwelling‐favorable northerly wind, except during a brief neap tide period. Numerical experiments showed that the incoming Poincaré wave tide from the East China Sea plays a key role in forming this counter‐wind transport system. This tidal wave produces a shoreward tidal stress south of 33.5°N in the inner southwestern Yellow Sea, driving an upshelf transport under the Earth's rotation. Counterpropagating tidal waves from the East China Sea and the northern Yellow Sea collide in coastal water in 32.5–34°N, which produce a standing tidal wave and therefore a mean sea‐surface setup with alongshore and cross‐shelf scales of both >100 km. This sea‐surface setup causes an alongshore sea surface gradient, which veers the upshelf transport to the offshore direction under geostrophic balance. The strong tidal current increases the tidal‐mean bottom resistance in the SCW, thus reduces the wind‐driven current to a magnitude smaller than the tide‐induced residual transport velocity. Therefore, upshelf transport persists in the inner southwestern Yellow Sea, and the Changjiang River Estuary becomes a major source area for the inner southwestern Yellow Sea. Key Points: Coastal current is reversed by shoreward tide stress under a Poincaré; wave tide Wind‐driven current is damped due to the enhanced tidal‐mean bottom resistance Changjiang Estuary is source area for inner southwestern Yellow Sea in winter season