Publication Date:
2022-05-26
Description:
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): C03033, doi:10.1029/2011JC007150.
Description:
The high-resolution, unstructured grid Finite-Volume Community Ocean Model (FVCOM) was used to examine the physical mechanisms that cause current separation and upwelling over the southeast shelf of Vietnam in the South China Sea (SCS). Process-oriented experiments suggest that the southwesterly monsoon wind is a key physical mechanism for upwelling in that area but not a prerequisite to cause current separation. With no wind forcing, current separation in summer can occur as a result of the encounter of a southward along-shelf coastal current from the north and northeastward buoyancy-driven and stratified tidal-rectified currents from the southwest. The southward current can be traced upstream to the Hong River in the Gulf of Tonkin. This current is dominated by semigeostrophic dynamics and is mostly confined to the narrow shelf along the northern Vietnamese coast. The northeastward currents are generated by tidal rectification and are intensified by the Mekong River discharge and southwesterly monsoon wind forcing. The dynamics controlling this current are fully nonlinear, with significant contributions from advection and vertical turbulent mixing. Upwelling in the current separation zone can be produced by a spatially uniform constant wind field and can be explained using simple wind-induced Ekman transport theory. This finding differs from previous theory in which the regional dipole wind stress curl is claimed as a key mechanism for current separation and upwelling in this coastal region. Our SCS FVCOM, driven by the wind stress, river discharge, and tides, is capable of reproducing the location and tongue-like offshore distribution of temperature as those seen in satellite-derived sea surface temperature imagery.
Description:
This work was supported by an Office of
Naval Research grant through a subcontract from the Woods Hole
Oceanographic Institution (WHOI). The development of
FVCOM was supported by the NSF Ocean Sciences Division through grants
OCE-0234545, OCE-0227679, OCE-0606928, OCE-0712903, OCE-
0726851, and OCE-0814505; the NSF Office of Polar Programs-Arctic
Sciences Division through grants ARC0712903, ARC0732084, and
ARC0804029; MIT Sea Grant projects 2006-RC-103 and 2010-R/RC-
116; and the NOAA NERACOOS program for the UMASS Dartmouth
team. C. Chen’s contribution is also supported by the Shanghai Ocean University
International Cooperation Program (A-2302-11-0003), the Program
of Science and Technology Commission of Shanghai Municipality
(09320503700), the Leading Academic Discipline Project of Shanghai
Municipal Education Commission (project J50702), and Zhi Jiang Scholar
and 111 project funds of the State Key Laboratory for Estuarine and
Coastal Research, East China Normal University. Z. Lai’s contribution is
supported by the China MOST Project 2012CB956004 SYSU 985, grant
42000-3181302.
Description:
2012-09-21
Keywords:
South China Sea
;
Current separation
;
Upwelling
Repository Name:
Woods Hole Open Access Server
Type:
Article
Format:
application/pdf
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