Observational evidence for tidal straining over a sloping continental shelf

Endoh, Tatsuo; Yoshikawa, Yutaka; Matsuno, Takeshi; Wakata, Yoshinobu; Lee, Keun Jong; Umlauf, Lars

doi:10.1016/j.csr.2016.01.018

Cited by 11 publications

(26 citation statements)

References 25 publications

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“…It was found that sediment can be transported over several kilometers during one tidal cycle, and that tidal pumping is the most important driver for this transport. After observational evidence for the occurrence of slope-induced tidal straining have been found on a continental shelf in the East China Sea (Endoh et al, 2016), this idealized, one-dimensional model was extended to include the effect of Earth rotation. …”

Section: Resultsmentioning

confidence: 99%

Book of Abstracts NCK days 2017, 15 – 17 March, Royal Netherlands Naval College (KIM) – Den Helder

Groot

Vries²,

Arens³

et al. 2017

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Section: Resultsmentioning

confidence: 99%

Book of Abstracts NCK days 2017, 15 – 17 March, Royal Netherlands Naval College (KIM) – Den Helder

Groot

Vries²,

Arens³

et al. 2017

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“…Endoh et al . [] pointed out that this large spatial separation, and the fact that the less dense river water will mainly affect the near‐surface layer during the thermally stratified summer period, suggests that the BBL at position S is unlikely to be dynamically influenced by freshwater runoff.…”

Section: Study Site and Methodsmentioning

confidence: 99%

“…First observational evidence for slope‐induced tidal straining was recently discussed by Endoh et al . [], who analyzed an extensive data set, including turbulence microstructure observations, from a topographic slope exposed to strong tidal currents in the East China Sea. These authors described a periodic destabilization of the water column during periods with upslope tidal currents, induced by the presence of a persistent cross‐slope density gradient.…”

Section: Introductionmentioning

confidence: 99%

“…Here we attempt to clarify the mechanisms, implications, and relevance of slope‐induced tidal straining on a real oceanic shelf by combining the results from previous modeling studies by Umlauf and Burchard [] and Schulz and Umlauf [] with the experimental data by Endoh et al . []. In section 2, we extend the model used by Schulz and Umlauf [] to include the effects of rotation before we briefly summarize the field observations discussed by Endoh et al .…”

Section: Introductionmentioning

confidence: 99%

“…In section 2, we extend the model used by Schulz and Umlauf [] to include the effects of rotation before we briefly summarize the field observations discussed by Endoh et al . [] in section 3. After deriving model parameters from these observations in section 4, we present the model results in section 5, and compare them to the field data. The implications of tidal straining for the generation of residual currents and the residual transport of suspended material are analyzed in section 6 before we provide a short discussion of our results and draw some conclusions in section 7.…”

Section: Introductionmentioning

confidence: 99%

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Slope‐induced tidal straining: Analysis of rotational effects

2017

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Tidal straining is known to be an important factor for the generation of residual currents and transports of suspended matter in the coastal ocean. Recent modeling studies and field experiments have revealed a new type of “slope‐induced” tidal straining, in which the horizontal density gradient required for this process is induced by the presence of a slope rather than by river runoff (as in classical tidal straining). Slope‐induced tidal straining is investigated here with the help of an idealized numerical model, and results are compared to a recent data set from the East China Sea providing first direct observational evidence. The focus of this study is on the effect of rotation that was ignored in previous investigations. The model is shown to reproduce the key features of the observations, in particular the strain‐induced generation of unstable stratification in the bottom boundary layer during periods of upslope flow. Rotation effects are found to significantly reduce the upslope tidal pumping of suspended material and also give rise to a newly identified pumping mechanism that results in a vigorous transport of suspended material along the slope. It is shown that slope‐induced tidal straining is likely to be relevant for a wide range of oceanic slopes exposed to tidal motions.

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Observations of Tidal Straining Within Two Different Ocean Environments in the East China Sea: Stratification and Near‐Bottom Turbulence

2017

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Tidal straining describes the straining effect induced by the vertical shear of oscillatory tidal currents that act on horizontal density gradients. It tends to create tidal periodic stratification and modulate the turbulence in the bottom boundary layer (BBL). Here, we present observations of current, hydrology and turbulence obtained at two mooring stations that are characterized by two typical hydrological environments in the East China Sea (ECS). One is located adjacent to the Changjiang River's mouth, and the other is located over a sloping shelf which is far from the freshwater sources. Tidal straining induces a semidiurnal switching between stable and unstable stratification at both stations. Near‐bottom high‐frequency velocity measurements further reveal that the dissipation rate of turbulent kinetic energy (TKE) is highly elevated during periods when unstable stratification occurs. A comparison between the TKE dissipation rate ( ɛ) and the shear production ( P) further reveals that the near‐bottom mixing is locally shear‐induced most of the time except during the unstable stratification period. Within this period, the magnitude of dissipation exceeds the expected value based on the law of the wall by an order of magnitude. The buoyancy flux that calculated by the balance method is too small to compensate for the existing discrepancy between the dissipation and shear production. Another plausible candidate is the advection of TKE, which may play an important role in the TKE budget during the unstable stratification period.

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Observational evidence for tidal straining over a sloping continental shelf

Cited by 11 publications

References 25 publications

Book of Abstracts NCK days 2017, 15 – 17 March, Royal Netherlands Naval College (KIM) – Den Helder

Book of Abstracts NCK days 2017, 15 – 17 March, Royal Netherlands Naval College (KIM) – Den Helder

Slope‐induced tidal straining: Analysis of rotational effects

Observations of Tidal Straining Within Two Different Ocean Environments in the East China Sea: Stratification and Near‐Bottom Turbulence

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