Coupled External‐Internal Dynamics of Layered Circulation in the South China Sea: A Modeling Study

Cai, Zheng-Li; Gan, Jianping

doi:10.1029/2019jc014962

Cited by 13 publications

(15 citation statements)

References 29 publications

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“…Our analyses (Supplementary Fig. 2 ) showed that an additional contribution of positive in the upper layer forms in LS because of the westward influx of positive relative vorticity on the western side of the Kuroshio jet and because there is a larger kinetic energy ( KE ) gradient 22 (see Eq. ( 7 ) in Methods section).…”

Section: Discussionmentioning

confidence: 94%

“…We found that the layered CAC circulation does not exist in an isopycnal coordinate system (Fig. 1d ) where the Stokes’ circulation has a different physical meaning with when the circulation is viewed at the geopotential levels 22 , 23 . Our results show that the difference of circulations defined in geopotential and isopycnal coordinates is particularly significant over the continental slope where change of isopycnal depth is dramatic.…”

Section: Introductionmentioning

confidence: 91%

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Hotspots of the stokes rotating circulation in a large marginal sea

et al. 2022

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Marginal seas, surrounded by continents with dense populations, are vulnerable and have a quick response to climate change effects. The seas typically have alternatively rotating layered circulations to regulate regional heat and biogeochemical transports. The circulations are composed of dynamically active hotspots and governed by the couplings between unique extrinsic inflow and intrinsic dynamic response. Ambiguities about the circulations’ structure, composition, and physics still exist, and these ambiguities have led to poor numerical simulation of the marginal sea in global models. The South China Sea is an outstanding example of a marginal sea that has this typical rotating circulation. Our study demonstrates that the rotating circulation is structured by energetic hotspots with large vorticity arising from unique dynamics in the marginal sea and is identifiable by the constraints of Stokes Theorem. These hotspots contribute most of the vorticity and most of energy needed to form and maintain the rotating circulation pattern. Our findings provide new insights on the distinguishing features of the rotating circulation and the dominant physics with the objectives of advancing our knowledge and improving modeling of marginal seas.

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Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 91%

Hotspots of the stokes rotating circulation in a large marginal sea

et al. 2022

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“…The contribution of vertical motion to vorticity change in the CAC circulation can be illustrated by layer‐integrated vorticity dynamics (Cai & Gan, 2019; Gan, Liu, & Hui, 2016),

\nabla \times \int_{L_{b}}^{L_{u}} \frac{\partial {\overset{true\to}{V}}_{h}}{\partial t} italicdz = \nabla \times \int_{L_{b}}^{L_{u}} \underset{\underset{⏟}{- \overset{true\to}{V} \cdot \nabla {\overset{V}{true}}_{h}}}{true} italicdz + \nabla \times \int_{L_{b}}^{L_{u}} \underset{PGF}{\underset{⏟}{\frac{- 1}{ρ_{0}} \nabla_{h} P}} italicdz - \nabla \cdot \int_{L_{b}}^{L_{u}} f {\overset{true\to}{V}}_{h} italicdz + \nabla \times \int_{L_{b}}^{L_{u}} \underset{VVIS}{\underset{⏟}{{[K_{v} {((), {\overset{V}{true}}_{h})}_{z}]}_{z}}} italicdz,

where L u and L b are the geopotential depths at the top and bottom of each of the three layers.

\overset{V}{true}

is the velocity vector,

\overset{V_{h}}{true}

is the horizontal velocity vector, and v is the velocity in the meridional direction.…”

Section: The Numerical Model and Methodsmentioning

confidence: 99%

“…The contribution of vertical motion to vorticity change in the CAC circulation can be illustrated by layer-integrated vorticity dynamics (Cai & Gan, 2019;Gan, Liu, & Hui, 2016),…”

Section: The Numerical Model and Methodsmentioning

confidence: 99%

“…Using a three‐layer model, Quan and Xue (2018) illustrated that the layer thickness variation, which represents the vertical motion in a geopotential coordinate system, is the key to linking the upper and middle layers and to regulating the variability of the SCS basin circulation. Based on the process‐oriented numerical modeling, Cai and Gan (2019) proposed that the vertical vorticity flux associated with the divergence/convergence of water (

- f \nabla \cdot {\overset{true\to}{V}}_{h}

) plays a significant role in the vorticity balance in the semi‐closed middle and lower layers, which dynamically links the CAC circulation in the different layers and sustains the layered circulation.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of the Cross‐Layer Exchange for the Layered Circulation in the South China Sea

Cai

Gan

2020

JGR Oceans

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The cyclonic‐anticyclonic‐cyclonic (CAC) circulation in the upper (<750 m)‐middle (750–1,500 m)‐deep (>1,500 m) layers of South China Sea (SCS) is mainly driven by the extrinsic lateral vorticity flux due to inflow‐outflow‐inflow through the Luzon Strait (LS) and the associated intrinsic vertical exchange (VE) in the basin. The contribution of spatiotemporal structure of the VE through vortex stretching and squeezing to CAC circulation, which was unknown, mainly occurs in the semi‐closed middle and deep layers and has a strong seasonality. During summer, the vorticity flux induced by net upward VEs crossing the upper (750 m) and lower (1,500 m) interfaces of CAC circulation is equivalent to ~40% of the lateral vorticity flux for strengthening the anticyclonic and cyclonic circulation in the middle and deep layers, respectively. During winter, the net downward VE crossing the upper interface squeezes the middle layer and strengthens its anticyclonic circulation, while the net VE crossing the lower interface is too small to affect the circulation. The VE and its seasonality in the basin are largely governed by the cross‐isobath geostrophic transport (CGTb) due to interaction between along‐isobath circular currents and rugged slope topography. The CGTb is formed by the along‐isobath bottom pressure gradient associated with surface wind stress curl, nonlinear advection, and beta effect over the meandering slope topography. Our study revealed how important VE between the layers is to the CAC circulation itself, and our work advanced the understanding of the intrinsic‐extrinsic dynamic coupling that forms, develops, and sustains the CAC circulation in the SCS.

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Deep circulation in the South China Sea simulated in a regional model

Zhao

Zhou

et al. 2020

Ocean Dynamics

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Coupled External‐Internal Dynamics of Layered Circulation in the South China Sea: A Modeling Study

Cited by 13 publications

References 29 publications

Hotspots of the stokes rotating circulation in a large marginal sea

Hotspots of the stokes rotating circulation in a large marginal sea

Dynamics of the Cross‐Layer Exchange for the Layered Circulation in the South China Sea

Deep circulation in the South China Sea simulated in a regional model

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