Study of the dynamics of wind‐driven transports into the Yellow Sea during winter

Abstract

Synoptic wind stresses and surface heat flux force a three‐dimensional numerical ocean model of the Yellow Sea/East China Sea dynamics. The basin response to winter winds is examined through the model output fields. Northerly wind bursts are a frequent winter occurrence in this region. The wind bursts develop a southward flowing current along the Chinese coast as the wind stress forces fluid out of the Bohai Sea. A north‐south pressure gradient develops as surface water travels from the Bohai Sea southward, decreasing the elevation in the north relative to the elevation in the south. Also, a westward pressure gradient across the Yellow Sea basin develops in response to the wind forcing. The southward pressure gradient forces a bottom flow in the direction opposite to the wind stress. This return flow is concentrated in a deep trough located on the eastern side of the basin. After the northerly wind ceases the northward transport increases pressure in the north with the result of slowing or stopping the flow northward. At times, pressure increases in the north sufficiently to force a southward flow in the trough. Following strong northerly wind events, northward transport into the Yellow Sea occupies the entire trough and may extend into the northern Yellow Sea/Bohai Sea. During periods of calm winds, northward flow usually does not penetrate beyond 34°N in the Yellow Sea. This flow is northward on the western side of the island of Cheju. The flow turns eastward north of Cheju and then southward, passing through the Cheju‐Korea Strait. The wind stress along the Korean coast often deviates from the northerly wind stress over the rest of the Yellow Sea. Thus the flow along the Korean coast is not as closely related to the northerly wind bursts as the flow along the Chinese coast. The winter circulation in the Yellow Sea is predominately a barotropic response to winds with fluctuations due to Ekman flow.