Modeling Semidiurnal Internal Tide Variability in the Southern California Bight

Buijsman, Maarten C.; Uchiyama, Yusuke; McWilliams, James C.; Hill-Lindsay, C. R.

doi:10.1175/2011jpo4597.1

Cited by 58 publications

(81 citation statements)

References 44 publications

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“…In the case of the south, where the topography was subcritical (g/c < 1) and the first mode was dominant, it appears that the baroclinic energy generated on the shelf break or the Biobío canyon should propagate toward the coast. Therefore, our observational results for Coquimbo and Concepcion resemble theoretical cases studied by Muller and Liu [2000] and Buijsman et al [2012].…”

Section: Baroclinic Semidiurnal Tidal Currentssupporting

confidence: 79%

“…In the case of Coquimbo, the fluctuations were not only associated with the first dynamic mode but also with the second and third modes. Buijsman et al [2012], using a numerical model in the Southern California Bight, showed that the energy of semidiurnal internal waves generated over the continental slope was reflected toward the ocean. Some energy associated with high mode-numbers, however, propagated toward the coast when the topography was supercritical (ratio of slope bathymetry (g) and slope internal waves (c) is higher than 1, g/c > 1).…”

Section: Baroclinic Semidiurnal Tidal Currentsmentioning

confidence: 99%

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Barotropic and baroclinic semidiurnal tidal currents in two contrasting coastal upwelling zones of Chile

et al. 2013

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[1] Current velocity observations from the continental shelves of Coquimbo (~30 S) and Concepcion (~36 30'S), central Chile, were analyzed to evaluate the role of water column stratification and shelf width on baroclinic semidiurnal tidal currents. Semidiurnal barotropic currents off both zones were typically < 5 cm/s, but depth-dependent semidiurnal flows could exceed 10 cm s -1 during stratified conditions. Both zones are recognized as pronounced upwelling centers, with maximum upwelling-favorable winds in spring and summer, respectively. At the northern zone, stratification was mainly controlled by temperature differences between surface and bottom waters with maximum stratification during summer. The southern zone showed more stratification during winter because of freshwater input from local rivers. Consequently, greater variability in the baroclinic semidiurnal currents was observed during summer at the northern continental shelf and in winter at the south. In both regions, much of the semidiurnal variability was consistent with an internal wave's first baroclinic mode of wavelengths of~10-13 km. Nevertheless, during the period of maximum energy fluxes off the north, the second baroclinic mode (wavelength~7 km) was also important and matched periods of low upwelling index (relaxation of upwelling favorable winds). Typical energy fluxes during summer integrated in the water column, related to the semidiurnal internal tides were 0.12 W/m of the northern site and 0.1 W/m off the southern site. Possible sites of internal wave generation off the south were the Biobío submarine canyon and the slope/shelf break, while off the north, the generation site was the slope/shelf break.

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Section: Baroclinic Semidiurnal Tidal Currentssupporting

confidence: 79%

Section: Baroclinic Semidiurnal Tidal Currentsmentioning

confidence: 99%

Barotropic and baroclinic semidiurnal tidal currents in two contrasting coastal upwelling zones of Chile

et al. 2013

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“…Baroclinic tides are primarily oriented in the horizontal direction and arises almost entirely from gradients in the hydrostatic pressure (Carter et al, ). As a result, the hydrostatic ROMS has been widely utilized for regional ocean baroclinic tidal modeling (Buijsman et al, ; Dunphy et al, ; Powell et al, ; Robertson, , ; Robertson & Ffield, ; Xu, Liu, et al, ). Because of the implicit diffusion in the upstream‐biased advection scheme, the explicit lateral viscosity and diffusivity are null everywhere in the current model, except in the sponge layers near the open boundaries, where they increase smoothly on a few grid points.…”

Section: Numerical Simulationmentioning

confidence: 99%

Seasonal and Spatial Features of Barotropic and Baroclinic Tides in the Northwestern South China Sea

Tong

Jing

et al. 2020

JGR Oceans

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Seven seasonal moorings distributed over the shelf and slope east of Hainan Island and south of western Guangdong Province are used to investigate the seasonal characteristics of barotropic and baroclinic tides in the northwestern South China Sea (NWSCS). The barotropic K 1 current intensified during summer over the shelf sites. The diurnal baroclinic tides are much more prominent than the semidiurnal tides at each mooring site. Over the continental shelf, accompanied by large phase speeds and wavelengths, baroclinic tides are significantly enhanced in summer whereas they decrease to minimum values in winter when the water column is vertically well mixed, suggesting the key role of seasonal stratification in modulating the seasonal variation of baroclinic tide. To aid in elucidating these observations, a circulation-tide coupled model covering the whole South China Sea (SCS) is set up for baroclinic tidal energetics in the NWSCS. Comparisons with moorings, tidal gauges, altimeters, and so on show that the model reasonably predicts the barotropic and baroclinic tides and seasonal upper circulations in the SCS and NWSCS. The model results present significant summer intensification of barotropic K 1 energy in the NWSCS, which is in accordance with the observed summer-enhanced barotropic K 1 current. Strong baroclinic tides are reproduced over the summer shelf, which is related to intense stratification. The slope south of Hainan Island is a major local generation source for diurnal baroclinic tides that radiate southeastward approximately 500 km away. Both the Xisha Islands and Shenhu-Yitong shoals act as baroclinic tidal energy sink subregions. Plain Language Summary The South China Sea (SCS) is a semienclosed marginal basin wherethe diurnal barotropic tide is amplified because of the resonance, and the baroclinic tide is extremely active. Previous studies on baroclinic tides in the SCS mainly focused on the northeastern SCS and Luzon Strait. Due to limited in situ observations, the basic characteristics of baroclinic tides and their seasonality in the northwestern SCS (NWSCS) are rarely reported. Past sporadic research has demonstrated the existence of baroclinic tides in the Xisha Islands and northeastern shelf of Hainan Island by short-term observations. In the present paper, a large amount of in situ data, including seven seasonal ADCPs and CTDs, is used to identify the seasonal characteristics of barotropic and baroclinic tides over the shelf and slope east of Hainan Island and the shelf southeast of western Guangdong Province. Subsequently, a high-resolution circulation-tide coupled ocean model for SCS is used to analyze the seasonal distribution of baroclinic tide energetics in the NWSCS. Multiple sources, integrated baroclinic tidal energy fluxes and energy budgets for three important subregions, are identified by the model results, which have been validated with diverse data sets.

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“…Over the deep OR continental slope, Kelly et al (2012) find significant internal tide generation from along-slope currents interacting with along-slope topographic variations, leading to strong gradients in F E over the 10-km scales that characterize the underlying topographic variability. In semienclosed basins, the refraction, reflection, and scattering of internal tide energy can work to create resonances or basin-scale modes (e.g., Buijsman et al 2012) that alter the resultant wavefield (Guo et al 2011). …”

Section: Relating Nliw Occurrence To Shelfbreak Dynamicsmentioning

confidence: 99%

The Unpredictable Nature of Internal Tides on Continental Shelves

Nash

Kelly

Shroyer

et al. 2012

Journal of Physical Oceanography

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Packets of nonlinear internal waves (NLIWs) in a small area of the Mid-Atlantic Bight were 10 times more energetic during a local neap tide than during the preceding spring tide. This counterintuitive result cannot be explained if the waves are generated near the shelf break by the local barotropic tide since changes in shelfbreak stratification explain only a small fraction of the variability in barotropic to baroclinic conversion. Instead, this study suggests that the occurrence of strong NLIWs was caused by the shoaling of distantly generated internal tides with amplitudes that are uncorrelated with the local spring-neap cycle. An extensive set of moored observations show that NLIWs are correlated with the internal tide but uncorrelated with barotropic tide. Using harmonic analysis of a 40-day record, this study associates steady-phase motions at the shelf break with waves generated by the local barotropic tide and variable-phase motions with the shoaling of distantly generated internal tides. The dual sources of internal tide energy (local or remote) mean that shelf internal tides and NLIWs will be predictable with a local model only if the locally generated internal tides are significantly stronger than shoaling internal tides. Since the depth-integrated internal tide energy in the open ocean can greatly exceed that on the shelf, it is likely that shoaling internal tides control the energetics on shelves that are directly exposed to the open ocean.

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Modeling Semidiurnal Internal Tide Variability in the Southern California Bight

Cited by 58 publications

References 44 publications

Barotropic and baroclinic semidiurnal tidal currents in two contrasting coastal upwelling zones of Chile

Barotropic and baroclinic semidiurnal tidal currents in two contrasting coastal upwelling zones of Chile

Seasonal and Spatial Features of Barotropic and Baroclinic Tides in the Northwestern South China Sea

The Unpredictable Nature of Internal Tides on Continental Shelves

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