This research conducts modeling studies to explore shelf dynamics in the East China Sea (ECS). Two critical scientific topics, related to influences of Kuroshio to the shelf circulation and intrinsic dynamics underlying the flow-topography interactions in the ECS are addressed. Adapting long-term satellite altimetry observations and from sensible definitions of axis and transports in stream-coordinate, this study presents the "shore-side-boundary" of Kuroshio to investigate its true invasion to the ECS, which chiefly occurs southwest of Kyushu and the year-round intrusive transport is ~1.8 Sv. This important branch of the intrusion has not been resolved when the 200 m isobath was used to define the intrusion of Kuroshio into the ECS. A three-dimensional, limited-area numerical m...[ Read more ]

This research conducts modeling studies to explore shelf dynamics in the East China Sea (ECS). Two critical scientific topics, related to influences of Kuroshio to the shelf circulation and intrinsic dynamics underlying the flow-topography interactions in the ECS are addressed. Adapting long-term satellite altimetry observations and from sensible definitions of axis and transports in stream-coordinate, this study presents the "shore-side-boundary" of Kuroshio to investigate its true invasion to the ECS, which chiefly occurs southwest of Kyushu and the year-round intrusive transport is ~1.8 Sv. This important branch of the intrusion has not been resolved when the 200 m isobath was used to define the intrusion of Kuroshio into the ECS. A three-dimensional, limited-area numerical model with realistic shelf topography is developed to investigate the dynamical mechanism that leads to intensified summer upwelling in the lee of Zhoushan Islands and at the head of a submerged valley in the northwestern ECS. The upwelling, evidenced by intense upslope invasions of deep dense waters from both field measurements and the simulated results, is geostrophically strengthened by a counter-current pressure gradient force (PGF). The novel explanation derived from the vorticity and momentum analyses in this study finds that this PGF is generated by the net stress curl in the water column arising mainly from the bottom shear vorticity at the seaside of the upwelling jet. This negative PGF, and the associated shoreward transport, is further intensified by contributions of anti-cyclonic curvature vorticity to the net stress curl and by intense nonlinear advection of relative vorticity. This study develops an "active" OBC to be used in simulating the responses of summer upwelling to the tidal forcing. Although the wind-driven circulation in the ECS is suppressed by the intense tidal mixing, this study finds that the natures of the upwelling circulation are largely preserved.