scholarly journals Circulation Driven by Multihump Turbulent Mixing Over a Seamount in the South China Sea

2022 ◽  
Vol 8 ◽  
Author(s):  
Ruijie Ye ◽  
Xiaodong Shang ◽  
Wei Zhao ◽  
Chun Zhou ◽  
Qingxuan Yang ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Deep Water ◽  
Turbulent Mixing ◽  
Three Dimensional ◽  
The South China Sea ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
China Sea ◽  
Meridional Overturning

Turbulent mixing above rough topography is crucial for the vertical motions of deep water and the closure of the meridional overturning circulation. Related to prominent topographic features, turbulent mixing not only exhibits a bottom-intensified vertical structure but also displays substantial lateral variation. How turbulent mixing varies in the upslope direction and its impact on the upwelling of deep water over sloping topography remains poorly understood. In this study, the notable multihump structure of the bottom-intensified turbulent diffusivity in the upslope direction of a seamount in the South China Sea (SCS) is revealed by full-depth fine-resolution microstructure and hydrographic profiles. Numerical experiments indicate that multihump bottom-intensified turbulent mixing around a seamount could lead to multiple cells of locally strengthened circulations consisting of upwelling (downwelling) motions in (above) the bottom boundary layer (BBL) that are induced by bottom convergence (divergence) of the turbulent buoyancy flux. Accompanied by cyclonic (anticyclonic) flow, a three-dimensional spiral circulation manifests around the seamount topography. These findings regarding the turbulent mixing and three-dimensional circulation around a deep seamount provide support for the further interpretation of the abyssal meridional overturning circulation.

scholarly journals On the near-inertial variations of meridional overturning circulation in the South China Sea

Ocean Science ◽  
2016 ◽  
Vol 12 (1) ◽  
pp. 335-344 ◽  
Author(s):  
Jingen Xiao ◽  
Qiang Xie ◽  
Dongxiao Wang ◽  
Lei Yang ◽  
Yeqiang Shu ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Maximum Amplitude ◽  
Luzon Strait ◽  
The South China Sea ◽  
Meridional Overturning Circulation ◽  
The South ◽  
Overturning Circulation ◽  
China Sea ◽  
Meridional Overturning

Abstract. We examine near-inertial variability of the meridional overturning circulation in the South China Sea (SCSMOC) using a global 1 / 12° ocean reanalysis. Based on wavelet analysis and power spectrum, we suggest that deep SCSMOC has a significant near-inertial band. The maximum amplitude of the near-inertial signal in the SCSMOC is nearly 4 Sv. The spatial structure of the signal features regularly alternating counterclockwise and clockwise overturning cells. It is also found that the near-inertial signal of SCSMOC mainly originates from the region near the Luzon Strait and propagates equatorward at a speed of 1–3 m s−1. Further analyses suggest that the near-inertial signal in the SCSMOC is triggered by high-frequency wind variability near the Luzon Strait, where geostrophic shear always exists due to Kuroshio intrusion.

Progress on deep circulation and meridional overturning circulation in the South China Sea

2016 ◽  
Vol 59 (9) ◽  
pp. 1827-1833 ◽  
Author(s):  
DongXiao Wang ◽  
JinGen Xiao ◽  
YeQiang Shu ◽  
Qiang Xie ◽  
Ju Chen ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Meridional Overturning Circulation ◽  
The South ◽  
Overturning Circulation ◽  
China Sea ◽  
Deep Circulation ◽  
Meridional Overturning

scholarly journals The near-inertial variability of meridional overturning circulation in the South China Sea as shown by an eddy-resolving ocean reanalysis

2015 ◽  
Vol 12 (5) ◽  
pp. 2123-2146
Author(s):  
J. Xiao ◽  
D. Wang ◽  
Q. Xie ◽  
Y. Shu ◽  
C. Liu ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Luzon Strait ◽  
The South China Sea ◽  
Meridional Overturning Circulation ◽  
The South ◽  
Overturning Circulation ◽  
Ocean Reanalysis ◽  
China Sea ◽  
Meridional Overturning

Abstract. The near-inertial variability of the meridional overturning circulation in the South China Sea (SCSMOC) has been analyzed based on a global 1/12° ocean reanalysis. The wavelet analysis and power spectrum of deep SCSMOC time series shows that there is a significant signal in the near-inertial band. The maximum amplitude of the near-inertial signal in the SCSMOC is nearly 4 Sv. The spatial structure of the signal features regularly alternating counterclockwise and clockwise overturning cells. It is also found that the near-inertial signal of SCSMOC mainly originates from the Luzon Strait and propagates equatorward with the speed of 1–3 m s−1. Further analyses suggest that the near-inertial signal in the SCSMOC is triggered by high-frequency wind variability near the Luzon Strait where geostrophic shear always exists due to Kuroshio intrusion.

scholarly journals The shallow meridional overturning circulation of the South China Sea

2014 ◽  
Vol 11 (2) ◽  
pp. 1191-1212 ◽  
Author(s):  
N. Zhang ◽  
J. Lan ◽  
F. Cui
Keyword(s):  
South China Sea ◽  
Formation Mechanism ◽  
Wind Stress ◽  
Mixed Layer ◽  
South China ◽  
Open Ocean ◽  
The South China Sea ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
Meridional Overturning

Abstract. In this paper, the structure and formation mechanism of the annual-mean shallow meridional overturning circulation of the South China Sea (SCS) are investigated. A distinct clockwise overturning circulation is present above 400 m in the SCS on the climatological annual mean scale. The shallow meridional overturning circulation consists of downwelling in the northern SCS, a southward subsurface branch supplying upwelling in the southern SCS and a northward return flow of surface water. The formation mechanism is explored by studying causes of the branches constituting the meridional overturning circulation. The surface branch is driven by the annual mean zonal component of the wind stress which is predominantly westward. Another effect of the wind is Ekman pumping related subduction in the north hence the main source of downwelling there. The mixed layer depth reaches its maximum in winter and shoals in spring, which causes the thermocline to outcrop and ventilate. Part of the water mass from the bottom of the mixed layer subducts into the thermocline and flows southward along the isopycnals. The upwelling region is mainly along the Vietnam coast and in the open-ocean off it. In summer, the alongshore component of wind stress off Vietnam can cause coastal upwelling and the increase of alongshore wind off the coast can also cause great upwelling in the open-ocean off the Vietnam coast.

scholarly journals Three-Dimensional Distribution of Turbulent Mixing in the South China Sea

2016 ◽  
Vol 46 (3) ◽  
pp. 769-788 ◽  
Author(s):  
Qingxuan Yang ◽  
Wei Zhao ◽  
Xinfeng Liang ◽  
Jiwei Tian
Keyword(s):  
South China Sea ◽  
South China ◽  
Turbulent Mixing ◽  
Three Dimensional ◽  
Internal Tide ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Dimensional Distribution ◽  
First Time

AbstractA three-dimensional distribution of turbulent mixing in the South China Sea (SCS) is obtained for the first time, using the Gregg–Henyey–Polzin parameterization and hydrographic observations from 2005 to 2012. Results indicate that turbulent mixing generally increases with depth in the SCS, reaching the order of 10−2 m2 s−1 at depth. In the horizontal direction, turbulence is more active in the northern SCS than in the south and is more active in the east than the west. Two mixing “hotspots” are identified in the bottom water of the Luzon Strait and Zhongsha Island Chain area, where diapycnal diffusivity values are around 3 × 10−2 m2 s−1. Potential mechanisms responsible for these spatial patterns are discussed, which include internal tide, bottom bathymetry, and near-inertial energy.

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