Publisher： John Wiley & Sons Inc
E-ISSN： 2169-9291|120|4|2571-2587
ISSN： 2169-9275
Source： JOURNAL OF GEOPHYSICAL RESEARCH: OCEANS, Vol.120, Iss.4, 2015-04, pp. : 2571-2587
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Abstract
AbstractWe conducted a process‐oriented modeling study to investigate the characteristics and dynamics of the prominent upwelling over a vast submerged valley in the East China Sea (ECS). The valley is inversely funnel‐shaped with the west bank and the east bank oriented in the north‐south direction. A cross‐bank upward transport occurred along the west bank. It intensified northward and peaked around the head of the valley. An along‐bank southward pressure gradient force (PGF) formed the cross‐bank geostrophic transport for the upwelling over the valley. The PGF reached its maxima at the head of the valley. Our momentum and vorticity dynamic analyses revealed that a bottom stress curl mainly contributed the PGF along the west bank. At the same time, both the bottom stress curl and the nonlinear vorticity advection contributed to the PGF around the head. The bottom stress curl was due to the bottom shear vorticity of the coastal current and the curvature vorticity around the head. The nonlinear vorticity advection formed because of the vertical squeezing of vortex tube as the current flowed over the valley. The nonlinearity mainly affected the PGF around the head, whereas the bottom stress curl contributed to the PGF over the entire valley. The ratio of the nonlinear to frictional contributions to the PGF increased as the coastal current intensified. Our study demonstrates that the PGF that drives the upwelling over the valley is the combined result of the nonlinearity due to vertical squeezing of vortex tube and bottom frictional effects.
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