Intensified upwelling over a widened shelf in the northeastern South China Sea

Abstract

[1] Observational and three-dimensional modeling studies reveal that the intensified upwelling in the northeastern South China Sea (NSCS) is formed as a result of intensified upslope advection of dense deep waters that cross the middle shelf toward the inner shelf over a distinctly eastward widened shelf. The strongest advection occurs over the converging isobaths near the head of the widened shelf. As these dense deep waters advance shoreward, they are advected downstream by the quickly developed upwelling current over the inner shelf and eventually outcropped at the lee of a coastal cape. Dynamically, the shoreward cross-isobath transport over the widened shelf is geostrophically enhanced by a quasi-barotropic negative (westward) along-isobath pressure gradient force as a result of the net rate of the momentum influx and by an intensified bottom frictional transport owing to the flow confluence near the head of the widened shelf. A negative pressure gradient also exists at the lee of the coastal cape over the inner shelf and locally amplifies shoreward motion. Induced by the respective widened shelf and the coastal promontory, the along-isobath variations of cross-isobath transport in the water column over the middle and inner shelves interactively characterize intensified upwelling in the NSCS.

Seasonal variability of surface phytoplankton in the Northern South China Sea: A one-dimensional coupled physical-biogeochemical modeling study

“…Obviously, the study area is away from the previously reported coastal upwelling regions in the SCS (Shaw et al, 1996;Jing et al, 2009;Gan et al, 2009) but partly includes the South East Asia Time-Series Station (SEATS station, Wong et al, 2007). The bottom topography is relatively uniform with domain averaged depth >3500 m.…”

An eddy resolving tidal-driven model of the South China Sea assimilating along-track SLA data using the EnOI

“…In summer (not shown), tidal forcing weakens the continental shelf current, and influences the location and intensity of the upwelling maximum (i.e. Li, 1993;Austin and Lentz, 2002;Gan et al, 2009). This demonstrates the non-linear interaction between tides and mean currents and highlights the importance of tides for the main circulation of the SCS.…”

Phytoplankton response to a plume front in the northern South China Sea

“…Variability at the front is primarily controlled by the river discharge and by the direction and magnitude of the regional wind field (Dong et al, 2004). To the east of the PRE, the surface plume water can be entrained in the coastal current as a salinity tongue in the summer and propelled eastward and offshore by wind-driven jets to affect a large area of the NSCS shelf sea (Gan et al, 2009). …”