Layered model and insights into the vertical coupling of the South China Sea circulation in the upper and middle layers

Quan, Qi; Xue, Huijie

doi:10.1016/j.ocemod.2018.06.006

Cited by 14 publications

(17 citation statements)

References 46 publications

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“…The dynamical mechanism of the Banda Sea C‐CC‐C circulations is further explained based on the PV integral constraint as summarized in Figure : The upper layer (<500 m) circulation is clockwise, which is driven by a PV flux due to the net inward transport and Ekman pumping due to the clockwise wind stress curl on the annual mean basis; the counterclockwise (clockwise) circulation in the middle layer (bottom layer) is caused by the net outward (inward) transport of 0.48 Sv (−0.35 Sv). This relationship between the layered circulation and the inflows/outflows of the Banda Sea is similar to the one found in the South China Sea (Gan et al, ; Quan & Xue, ; Shu et al, ; Xu & Oey, ), albeit the circulation directions are reversed as the Banda Sea is in the Southern Hemisphere. The basin‐scale upwelling from the deep layer and the subduction from the upper layer (dashed arrows in Figure ) are required by the physical principle of mass conservation, which is in accordance with the view proposed by Van Aken et al ().…”

Section: Discussionsupporting

confidence: 84%

The Indonesian Throughflow and the Circulation in the Banda Sea: A Modeling Study

2019

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To investigate the relationship between the Indonesian ThroughFlow (ITF) and the Banda Sea circulation, we set up a high‐resolution ocean circulation model for the western Pacific and northern Indian Oceans. This well‐validated model demonstrates complex distributions of the along‐channel velocity in different straits, with vertically sheared flows in the Makassar and Maluku straits but horizontally sheared flows in the Halmahera, Timor, and Ombai straits. The model also reveals a three‐layer circulation pattern in the Banda Sea: clockwise, counterclockwise, and clockwise in the upper (<500 m), middle (500–2,250 m), and lower (>2,250 m) water column, respectively. The Lagrangian tracking code TRACMASS is used to diagnose the sources and sinks of Banda Sea waters. The backward/forward tracking experiment pinpoints the inflows/outflows in the straits surrounding the Indonesian Archipelago (IA), which directly affect the Banda Sea. These TRACMASS results imply active vertical exchanges in the Banda Sea, which result in fast flushing with a typical time scale of 8 years. Based on the profiles of net transport into and out of the Banda Sea estimated from the tracking experiments, the three‐layer circulations of the Banda Sea are dynamically explained in terms of the potential vorticity (PV) integral constraint: the PV flux across the boundary and the wind stress curl act in concert with approximately equal order of magnitude for the clockwise circulation in the upper layer, while the positive (negative) PV flux to the middle (bottom) layer corresponds to the counterclockwise (clockwise) circulation.

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Section: Discussionsupporting

confidence: 84%

The Indonesian Throughflow and the Circulation in the Banda Sea: A Modeling Study

2019

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“…( 14) to test the sensitivity of the SCS circulation to the mixing intensity. After taking the deep layer into account, the circulations in the upper and middle layers of the SCS are similar to those based on the three-layer model in our previous study (Quan and Xue 2018; not shown). For the deep layer, it is found that the basin-scale circulation is anticyclonic (Figs.…”

Section: A Impact Of Abyssal Mixing Intensity On the Scs Circulationsupporting

confidence: 78%

“…Hence, they become very useful tools to study the dynamical mechanism of the SCS circulation (e.g., Wang et al 2006;Cai et al 2007;Yang et al 2015). By adding the fourth layer to represent the abyssal SCS, the ocean model used here is further developed from our previous three-layer model (Quan and Xue 2018), which has been validated to well reproduce the SCS circulation in the upper and middle layers and reveal the dynamical coupling between them. Note that both models are modified from the layered Indian Ocean model Kundu 1988, 1989;McCreary et al 1993) and its ramification, the 4.5-layer SCS model (Yu et al 2007(Yu et al , 2008Yaremchuk et al 2009).…”

Section: A Layered Ocean Modelmentioning

confidence: 99%

Influence of Abyssal Mixing on the Multilayer Circulation in the South China Sea

Quan

Xue

2019

Journal of Physical Oceanography

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By parameterizing the abyssal mixing as the exchange velocity (entrainment/detrainment) between the middle and deep layers of the South China Sea (SCS), its effects on the multilayer circulation are examined. Results indicate that the cyclonic circulation in the deep SCS appears only when the mixing induces an entrainment of at least 0.72 Sv (1 Sv ≡ 106 m3 s−1) from the deep to the middle layer, which is equivalent to a diapycnal diffusivity of 0.65 × 10−3 m2 s−1 or a net input rate of gravitational potential energy (GPE) of 6.89 GW, respectively. It is also found that tidal mixing in the SCS is stronger than the threshold for the generation of the cyclonic abyssal circulation, but the pattern and evolution of the deep circulation and meridional overturning circulation also depend on the spatiotemporal variability of the mixing. Moreover, the abyssal mixing is able to intensify the anticyclonic circulation in the middle layer but weaken the cyclonic circulation in the upper layer. Vorticity analysis suggests that the upward net flux induced by the abyssal mixing leads to vortex stretching (squeezing) and modulates the pressure gradient by redistributing the layer thickness, hence affects the pattern and strength of the circulation in the middle (deep) layer of the SCS, respectively. The depth-integrated effect of the thickness variation can modulate the pressure gradient across all layers and hence influence the upper-layer circulation.

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“…For example, interactions between the TRWs and planetary Rossby waves probably account for the deep upwelling associated with meridional overturning circulation in the abyssal SCS (Shu et al., 2014). Moreover, TRWs and wave‐related mixing play a vital role in the generation and evolution of deep circulation in the SCS (Quan & Xue, 2019), as well as in the vertical coupling of the SCS circulation between the upper and middle layers (Quan & Xue, 2018). All these factors may lead to more active SCS circulation that could modulate the Indo‐Pacific exchange, thereby affecting the regional climate and ecosystem.…”

Section: Summary and Discussionmentioning

confidence: 99%

Influence of the Kuroshio Intrusion on Deep Flow Intraseasonal Variability in the Northern South China Sea

et al. 2021

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Interactions between the open ocean and marginal seas have been suggested to be critical to the redistribution and dissipation of global energy. Here, we propose a mechanism for the upper open ocean influencing the deep flow in marginal seas that hinges on the formation and propagation of topographic Rossby waves (TRWs). Observations and high‐resolution simulations suggest substantial intraseasonal variability with periods of 5–60 days associated with the deep flow over continental slopes of the northern South China Sea (NSCS). These fluctuations generally account for over 40% of the total deep kinetic energy variability and the number can reach 70% over the slopes to the west of the Luzon Strait, southwest of the Dongsha Islands, and northeast of the Xisha Islands. By examining the spatiotemporal features of the fluctuations, we demonstrate that the intraseasonal variability of the deep flow in the NSCS is closely associated with TRWs. Using a recently developed multiscale energetics analysis in combination with a ray tracing model, we show that the energy sources of TRWs can be traced back to the east of the Dongsha Islands, where the Kuroshio intrusion and related eddies energize the TRWs primarily through pressure work. These waves propagate westward across the NSCS and drive the intraseasonal variability of the deep flow over continental slopes. Our findings highlight an energy pathway from the open ocean western boundary current to the abyssal marginal sea that could modulate regional circulation as well as exchanges between major ocean basins.

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Layered model and insights into the vertical coupling of the South China Sea circulation in the upper and middle layers

Cited by 14 publications

References 46 publications

The Indonesian Throughflow and the Circulation in the Banda Sea: A Modeling Study

The Indonesian Throughflow and the Circulation in the Banda Sea: A Modeling Study

Influence of Abyssal Mixing on the Multilayer Circulation in the South China Sea

Influence of the Kuroshio Intrusion on Deep Flow Intraseasonal Variability in the Northern South China Sea

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