Island Wakes in Shallow Water

Cao, Yuhan; McWilliams, James C.

doi:10.1080/07055900.2018.1448750

Cited by 18 publications

(23 citation statements)

References 18 publications

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“…Dynamically, growth of submesoscales in region LS is mainly through barotropic instability that extracts KE from the background current (i.e., the BT term). The horizontally sheared flows responsible for the barotropic instability, in essence, are set up by the lateral and bottom boundary drags when the strong currents of Kuroshio and mesoscale eddies encounter the islands (Dong et al, , ; Srinivasan et al, ). As a result, temporal variation of the associated MSR is strongly modulated by the background KE here ( r = 0.79).…”

Section: Summary and Discussionmentioning

confidence: 99%

Spatiotemporal Characteristics and Generation Mechanisms of Submesoscale Currents in the Northeastern South China Sea Revealed by Numerical Simulations

Zhang

Qiu

et al. 2020

JGR Oceans

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Although both geostrophic‐balanced mesoscale eddies and unbalanced small‐scale processes have been well studied in the northeastern South China Sea (NE‐SCS), less attention has been devoted to the submesoscales in between (i.e., O(1–10 km)), which is recognized as an important conduit connecting the balanced and unbalanced motions. Based on the output from a 1/30° OGCM simulation, spatiotemporal characteristics and generation mechanisms of submesoscales in the NE‐SCS are investigated in this study. Through examining the submesoscale relative vorticity and vertical velocity, the regions southwest of Taiwan (ST) and Luzon Strait (LS) are identified as two hot spots of submesoscales in the NE‐SCS. Seasonally, the submesoscales in region ST are much stronger in winter than summer, while those in LS do not show a significant seasonality. Statistical analysis suggests that the strength of submesoscales in regions ST and LS is highly correlated with the product of mixed‐layer depth and mesoscale strain rate (MSR) and with the MSR itself, respectively. By conducting theoretical scaling and energetics analysis, the authors find that the mixed‐layer instability whose strength is determined by the combination of mixed‐layer depth and MSR and the barotropic instability associated with current‐islands interactions are the dominant generation mechanisms of submesoscales in the above two regions, respectively. Further examinations of the submesoscale energy budget indicate that, to keep a balanced state, the generated submesoscales have to be dissipated by a forward energy cascade, highlighting the important role of submesoscales in the energy balance of the NE‐SCS circulation.

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Section: Summary and Discussionmentioning

confidence: 99%

Spatiotemporal Characteristics and Generation Mechanisms of Submesoscale Currents in the Northeastern South China Sea Revealed by Numerical Simulations

Zhang

Qiu

et al. 2020

JGR Oceans

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“…Condition i was convincingly demonstrated by Dong et al (2007) by considering seamount flows with varying Re. Condition ii requires that the seamount height is no more than about 60% of the depth of the ocean, as described above in section 2b.…”

Section: Fig 2 a Seamount Database Frommentioning

confidence: 75%

“…The depth ratio has been demonstrated to be a controlling parameter in determining the vertical extent of the eddies (Boyer and Chen 1987;Srinivasan et al 2019); here it is maintained at a constant value of 0.6, which tends to limit the formation of Taylor column structures that exceed the height of the seamount. The Reynolds number is approximately 2000, which, in line with Dong et al (2007), may be assumed to faithfully allow the representation of the eddy processes in a Reynolds-number-independent manner. The Froude and Rossby numbers are manipulated by changing the Brunt-Väisälä frequency and Coriolis parameter, respectively.…”

Section: B Model Parameterizationmentioning

confidence: 99%

“…It has also been hypothesized that seamounts might act as ''stirring rods'' and contribute to water column mixing (Munk and Wunsch 1998). Yet, only recently there has been increased scientific interest in determining the wake dynamics associated with flow patterns past islands and seamounts, and associated energy extraction from the flow field (e.g., Dong et al 2007;Gula et al 2016;Dong et al 2018;Zeiden et al 2019;MacKinnon et al 2019). Rare measurements of seamount wakes in the South China Sea reveal deep energetic eddies with a baroclinic structure (Chen et al 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Numerical modeling offers an opportunity for a quantitative investigation into seamount wakes; regional models have proven to be effective methods of reproducing observed flow patterns near real topography (Beckmann and Haidvogel 1997;Coutis and Middleton 2002;Dong and McWilliams 2007;Boutov et al 2010). Traditionally, these models have been used within the context of understanding the hydrodynamics of a specific site, but they have the potential to offer more insight into the underlying physics when used with idealized settings.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Energetics of Seamount Wakes. Part I: Energy Exchange

Perfect

Kumar

Riley

2020

Journal of Physical Oceanography

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Seamounts have been theorized to act as “stirring rods,” converting barotropic flow into an unsteady wake, turbulence, and diapycnal mixing. The energetics of these processes are not well understood, but they may have implications for basin-scale mixing calculations. This study presents the results of a series of simulations for idealized seamounts in steady barotropic flow, with varying degrees of stratification and rotation. The kinetic energy within each simulation domain is decomposed into the mean kinetic energy, unsteady eddy energy, and turbulent kinetic energy; evolution equations are derived for each. Within the evolution equations, energy exchange terms arise, which relate the various forms of kinetic energy and potential energy. Key exchange terms, such as the rate at which the mean flow is converted into eddy energy, are compared across the Froude–Rossby parameter space. It is shown that the conversion terms associated with mesoscale motions are a function of the Burger number, which is consistent with a quasigeostrophic flow regime. Conversely, conversion terms associated with turbulent processes scale with the product of the Froude and Rossby number. The amount of energy extracted from the mean flows suggests that wake effects may be significant for the parameter range and model assumptions studied. These results suggest that some seamounts may indeed act as oceanic stirring rods.

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Island Mass Effect

Hasegawa

2019

Geophysical Monograph Series

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Island Wakes in Shallow Water

Cited by 18 publications

References 18 publications

Spatiotemporal Characteristics and Generation Mechanisms of Submesoscale Currents in the Northeastern South China Sea Revealed by Numerical Simulations

Spatiotemporal Characteristics and Generation Mechanisms of Submesoscale Currents in the Northeastern South China Sea Revealed by Numerical Simulations

Energetics of Seamount Wakes. Part I: Energy Exchange

Island Mass Effect

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