scholarly journals Impact of Channel Geometry and Rotation on the Trapping of Internal Tides

2007 ◽  
Vol 37 (11) ◽  
pp. 2740-2763 ◽  
Author(s):  
Sybren Drijfhout ◽  
Leo R. M. Maas
Keyword(s):  
Continental Slope ◽  
Three Dimensional ◽  
Tidal Energy ◽  
Ocean Model ◽  
Internal Tides ◽  
Open Boundary ◽  
Kelvin Wave ◽  
Channel Geometry ◽  
Channel Slope ◽  
The Cross

Abstract The generation and propagation of internal tides has been studied with an isopycnic three-dimensional ocean model. The response of a uniformly stratified sea in a channel, which is forced by a barotropic tide on its open boundary, is considered. The tide progresses into the channel and forces internal tides over a continental slope at the other end. The channel has a length of 1200 km and a width of 191.25 km. The bottom profile has been varied. In a series of four experiments it is shown how the cross-channel geometry affects the propagation and trapping of internal tides, and the penetration scale of wave energy, away from the continental slope, is discussed. In particular it is found that a cross-channel bottom slope constrains the penetration of the internal tidal energy. Most internal waves refract toward a cross-channel plane where they are trapped. The exception is formed by edge waves that carry part of the energy away from the continental slope. In the case of rotation near the continental slope, the Poincaré waves that arise in the absence of a cross-channel slope no longer bear the characteristics of the wave attractor predicted by 2D theory, but are almost completely arrested, while the right-bound Kelvin wave preserves the 2D attractor in the cross-channel plane, which is present in the nonrotating case. The reflected, barotropic right-bound Kelvin wave acts as a secondary internal wave generator along the cross-channel slope.

scholarly journals M2 tidal dynamics in the Ross Sea

2003 ◽  
Vol 15 (1) ◽  
pp. 41-46 ◽  
Author(s):  
ROBIN ROBERTSON ◽  
AIKE BECKMANN ◽  
HARTMUT HELLMER
Keyword(s):  
Continental Shelf ◽  
Ross Sea ◽  
Tidal Energy ◽  
Ocean Model ◽  
Internal Tides ◽  
Global Ocean ◽  
Tidal Dynamics ◽  
Tidal Elevation ◽  
Shelf Slope ◽  
Continental Shelf Slope

In certain regions of the Southern Ocean, tidal energy is believed to foster the mixing of different water masses, which eventually contribute to the formation of deep and bottom waters. The Ross Sea is one of the major ventilation sites of the global ocean abyss and a region of sparse tidal observations. We investigated M2 tidal dynamics in the Ross Sea using a three-dimensional sigma coordinate model, the Regional Ocean Model System (ROMS). Realistic topography and hydrography from existing observational data were used with a single tidal constituent, the semi-diurnal M2. The model fields faithfully reproduced the major features of the tidal circulation and had reasonable agreement with ten existing tidal elevation observations and forty-two existing tidal current measurements. The differences were attributed primarily to topographic errors. Internal tides were generated at the continental shelf/slope break and other areas of steep topography. Strong vertical shears in the horizontal velocities occurred under and at the edges of the Ross Ice Shelf and along the continental shelf/slope break. Estimates of lead formation based on divergence of baroclinic velocities were significantly higher than those based on barotrophic velocities, reaching over 10% at the continental shelf/slope break.

scholarly journals A parameterization of local and remote tidal mixing

2020 ◽  
Author(s):  
Casimir de Lavergne ◽  
Clément Vic ◽  
Gurvan Madec ◽  
Fabien Roquet ◽  
Amy Waterhouse ◽  
...  
Keyword(s):  
Vertical Mixing ◽  
Three Dimensional ◽  
Internal Tide ◽  
Ocean Model ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Global Ocean ◽  
Energy Conserving ◽  
Energy Constrained ◽  
Lagrangian Tracking

<p>Vertical mixing is often regarded as the Achilles’ heel of ocean models. In particular, few models include a comprehensive and energy-constrained parameterization of mixing by internal ocean tides. Here, we present an energy-conserving mixing scheme which accounts for the local breaking of high-mode internal tides and the distant dissipation of low-mode internal tides. The scheme relies on four static two-dimensional maps of internal tide dissipation, constructed using mode-by-mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global three-dimensional map of dissipation which compares well with available microstructure observations and with upper-ocean finestructure mixing estimates. Implemented in the NEMO global ocean model, the scheme improves the representation of deep water-mass transformation and obviates the need for a constant background diffusivity.</p>

scholarly journals An analytical study of <i>M</i><sub>2</sub> tidal waves in the Taiwan Strait using an extended Taylor method

Ocean Science ◽  
2018 ◽  
Vol 14 (1) ◽  
pp. 117-126 ◽  
Author(s):  
Di Wu ◽  
Guohong Fang ◽  
Xinmei Cui ◽  
Fei Teng
Keyword(s):  
Analytical Solution ◽  
Taiwan Strait ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Kelvin Wave ◽  
Deep Basin ◽  
Tidal Waves ◽  
Taylor Method ◽  
The Cross ◽  
The Taiwan Strait

Abstract. The tides in the Taiwan Strait (TS) feature large semidiurnal lunar (M2) amplitudes. An extended Taylor method is employed in this study to provide an analytical model for the M2 tide in the TS. The strait is idealized as a rectangular basin with a uniform depth, and the Coriolis force and bottom friction are retained in the governing equations. The observed tides at the northern and southern openings are used as open boundary conditions. The obtained analytical solution, which consists of a stronger southward propagating Kelvin wave, a weaker northward propagating Kelvin wave, and two families of Poincaré modes trapped at the northern and southern openings, agrees well with the observations in the strait. The superposition of two Kelvin waves basically represents the observed tidal pattern, including an anti-nodal band in the central strait, and the cross-strait asymmetry (greater amplitudes in the west and smaller in the east) of the anti-nodal band. Inclusion of Poincaré modes further improves the model result in that the cross-strait asymmetry can be better reproduced. To explore the formation mechanism of the northward propagating wave in the TS, three experiments are carried out, including the deep basin south of the strait. The results show that the southward incident wave is reflected to form a northward wave by the abruptly deepened topography south of the strait, but the reflected wave is slightly weaker than the northward wave obtained from the above analytical solution, in which the southern open boundary condition is specified with observations. Inclusion of the forcing at the Luzon Strait strengthens the northward Kelvin wave in the TS, and the forcing is thus of some (but lesser) importance to the M2 tide in the TS.

scholarly journals Modeling Assessment of Tidal Energy Extraction in the Western Passage

2020 ◽  
Vol 8 (6) ◽  
pp. 411
Author(s):  
Zhaoqing Yang ◽  
Taiping Wang ◽  
Ziyu Xiao ◽  
Levi Kilcher ◽  
Kevin Haas ◽  
...  
Keyword(s):  
Cross Sections ◽  
Numerical Models ◽  
Three Dimensional ◽  
Energy Resource ◽  
Field Measurements ◽  
Tidal Energy ◽  
Resource Assessment ◽  
Ocean Model ◽  
Energy Extraction ◽  
Technical Specifications

Numerical models have been widely used for the resource characterization and assessment of tidal instream energy. The accurate assessment of tidal stream energy resources at a feasibility or project-design scale requires detailed hydrodynamic model simulations or high-quality field measurements. This study applied a three-dimensional finite-volume community ocean model (FVCOM) to simulate the tidal hydrodynamics in the Passamaquoddy–Cobscook Bay archipelago, with a focus on the Western Passage, to assist tidal energy resource assessment. IEC Technical specifications were considered in the model configurations and simulations. The model was calibrated and validated with field measurements. Energy fluxes and power densities along selected cross sections were calculated to evaluate the feasibility of the tidal energy development at several hotspots that feature strong currents. When taking both the high current speed and water depth into account, the model results showed that the Western Passage has great potential for the deployment of tidal energy farms. The maximum extractable power in the Western Passage was estimated using the Garrett and Cummins method. Different criteria and methods recommended by the IEC for resource characterization were evaluated and discussed using a sensitivity analysis of energy extraction for a hypothetical tidal turbine farm in the Western Passage.

scholarly journals Tidal Energy Flows between the Midriff Islands in the Gulf of California

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 621
Author(s):  
Federico Angel Velazquez-Muñoz ◽  
Anatoliy Filonov
Keyword(s):  
Kinetic Energy ◽  
Internal Wave ◽  
Gulf Of California ◽  
Current Flow ◽  
Tidal Flow ◽  
Three Dimensional ◽  
Tidal Energy ◽  
Ocean Model ◽  
Field Development ◽  
Wave Measurements

The Gulf of California has many regions of potential tidal-stream energy that have been identified and characterized using in-situ measurements and numerical ocean models. The Midriff Islands region has received particular attention due to its increased current speeds and high kinetic energy. This increase in energy can be seen in the formation of internal wave packets propagating for several hundred kilometers. Here we present a brief description of internal wave measurements travel towards the Northern Gulf and explore energy generation sites. In this paper we characterize the tidal inflow and outflow that passes throughout the Midriff Islands in the central part of the Gulf. We use a three-dimensional numerical ocean model that adequately reproduces the tidal flow and the increase in speed and kinetic energy between the islands. The current flow structure shows the highest velocity cores near the shore and far from the bottom. During the rising tide, the maximum current flow (~0.6 ms−1) was found between Turón Island and San Lorenzo Island, from the surface to 200 m depth. When the currents flowed out of the Gulf, during the falling tide, the maximum negative current (−0.8 ms−1) was found between Tiburon Island and Turón Island, from near the surface to 80 m depth. Although there are favorable conditions for power generation potential by tidal flows, the vertical variability of the current must be considered for field development and equipment installation sites.

scholarly journals Model Estimates of M2 Internal Tide Generation over Mid-Atlantic Ridge Topography

2009 ◽  
Vol 39 (10) ◽  
pp. 2635-2651 ◽  
Author(s):  
N. V. Zilberman ◽  
J. M. Becker ◽  
M. A. Merrifield ◽  
G. S. Carter
Keyword(s):  
Internal Tide ◽  
Tidal Energy ◽  
Ocean Model ◽  
Equation Model ◽  
Internal Tides ◽  
Analytical Models ◽  
Topographic Slope ◽  
Conversion Rates ◽  
Mid Atlantic Ridge ◽  
Model Conversion

Abstract The conversion of barotropic to baroclinic M2 tidal energy is examined for a section of the Mid-Atlantic Ridge in the Brazil Basin using a primitive equation model. Model runs are made with different horizontal smoothing (1.5, 6, and 15 km) applied to a 192 km × 183 km section of multibeam bathymetry to characterize the influence of topographic resolution on the model conversion rates. In all model simulations, barotropic to baroclinic conversion is highest over near- and supercritical slopes on the flanks of abyssal hills and discordant zones. From these generation sites, internal tides propagate upward and downward as tidal beams. The most energetic internal tide mode generated is mode 2, consistent with the dominant length scales of the topographic slope spectrum (50 km). The topographic smoothing significantly affects the model conversion amplitudes, with the domain-averaged conversion rate from the 1.5-km run (15.1 mW m−2) 4% and 19% higher than for the 6-km (14.5 mW m−2) and 15-km runs (12.2 mW m−2), respectively. Analytical models for internal tide generation by subcritical topography predict conversion rates with modal dependence and spatial patterns qualitatively similar to the Princeton Ocean Model (POM) and also show a decrease in conversion with smoother topography. The POM conversion rates are approximately 20% higher than the analytical estimates for all model grids, which is attributed to spatial variations in the barotropic flow and near-bottom stratification over generation sites, which are incorporated in the model but not in the analytical estimates.

scholarly journals THREE-DIMENSIONAL SIMULATION OF TIDAL CURRENT IN LAMPUNG BAY: DIAGNOSTIC NUMERICAL EXPERIMENTS

2010 ◽  
Vol 3 (-) ◽  
Author(s):  
Alan Frendy Koropitan ◽  
Safwan Hadi ◽  
Ivonne M.Radjawane
Keyword(s):  
Tidal Current ◽  
Lower Layer ◽  
Three Dimensional ◽  
Ocean Model ◽  
Residual Current ◽  
Global Ocean ◽  
Open Boundary ◽  
Ocean Tide ◽  
Tidal Elevation ◽  
Diagnostic Mode

Princeton Ocean Model (POM) was used to calculate the tidal current in Lampung Bay using diagnostic mode. The model was forced by tidal elevation, which was given along the open boundary using a global ocean tide model-ORITIDE. The computed tidal elevation at St. 1 and St 2 are in a good agreement with the observed data, but the computed tidal current at St 1 at depth 2 m is not good and moderate approximation is showed at depth 10 m. Probably, it was influenced by non-linier effect of coastal geometry and bottom friction because of the position of current meter, mooring closed to the coastline. Generally, the calculated tidal currents in all layers show that the water flows into the bay during flood tide and goes out from the bay during ebb tide. The tidal current becomes strong when passing through the narrow passage of Pahawang Strait. The simulation of residual tidal current with particular emphasis on predominant contituent of M2 shows a strong inflow from the western part of the bay mouth, up to the central part of the bay, then the strong residual current deflects to the southeast and flows out from the eastern part of the bay mouth. This flow pattern is apparent in the upper and lower layer. The other part flows to the bay head and froms an antic lockwise circulation in the small basin region of the bay head. The anticlockwise circulations are showed in the upper layer and disappear in the layer near the bottom. Keywords: POM, diagnostic mode, tidal current, residual current, Lampung Ba.

scholarly journals Evaluation of an operational ocean model configuration at 1/12° spatial resolution for the Indonesian seas – Part 1: Ocean physics

2015 ◽  
Vol 8 (8) ◽  
pp. 6611-6668 ◽  
Author(s):  
B. Tranchant ◽  
G. Reffray ◽  
E. Greiner ◽  
D. Nugroho ◽  
A. Koch-Larrouy ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Satellite Data ◽  
Water Mass ◽  
Ocean Model ◽  
Internal Tides ◽  
Global Ocean ◽  
Open Boundary ◽  
Indonesian Throughflow ◽  
The South ◽  
Water Mass Transformation

Abstract. INDO12, a 1/12° regional version of the NEMO physical ocean model covering the whole Indonesian EEZ has been developed and is now running every week in the framework of the INDESO project (Infrastructure Development of Space Oceanography) implemented by the Indonesian Ministry of Marine Affairs and Fisheries. The initial hydrographic conditions as well as open boundary conditions are derived from the operational global ocean forecasting system at 1/4° operated by Mercator Ocean. Atmospheric forcing fields (3 hourly ECMWF analyses) are used to force the regional model. INDO12 is also forced by tidal currents and elevations, and by the inverse barometer effect. The turbulent mixing induced by internal tides is taken into account through a specific parameterization. In this study we evaluate the model skill through comparisons with various datasets including outputs of the parent model, climatologies, in situ temperature and salinity measurements, and satellite data. The simulated and altimeter-derived Eddy Kinetic Energy fields display similar patterns and confirm that tides are a dominant forcing in the area. The volume transport of the Indonesian ThroughFlow is in good agreement with the INSTANT current meter estimates while the transport through Luzon Strait is, on average, westward but probably too weak. Significant water mass transformation occurs along the main routes of the Indonesian Throughflow (ITF) and compares well with observations. Vertical mixing is able to erode the South and North Pacific subtropical waters salinity maximum as seen in TS diagrams. Compared to satellite data, surface salinity and temperature fields display marked biases in the South China Sea. Altogether, INDO12 proves to be able to provide a very realistic simulation of the ocean circulation and water mass transformation through the Indonesian Archipelago. A few weaknesses are also detected. Work is on-going to reduce or eliminate these problems in the second INDO12 version.

scholarly journals An analytical study on M<sub>2</sub> tidal wave in the Taiwan Strait with the extended Taylor's method

2017 ◽  
Author(s):  
Di Wu ◽  
Guohong Fang ◽  
Xinmei Cui ◽  
Fei Teng
Keyword(s):  
Analytical Solution ◽  
Taiwan Strait ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Kelvin Wave ◽  
Deep Basin ◽  
Secondary Importance ◽  
Friction Forces ◽  
The Cross ◽  
The Taiwan Strait

Abstract. The tides in the Taiwan Strait (TS) are featured by large M2 amplitudes. The extended Taylor's method is employed in this study to provide an analytical model for the M2 tide in the TS. The strait is idealized as a rectangular basin with a uniform depth, but the Coriolis and friction forces are retained in the governing equations. The observed tides at the northern and southern openings are used as open boundary conditions. The obtained analytical solution, which consists of a stronger southward propagating Kelvin wave, a weaker northward propagating Kelvin wave, and two families of Poincaré modes trapped at the northern and southern openings, agrees well with the observations in the strait. The superposition of two Kelvin waves can basically represent the observed tidal pattern, including an anti-nodal band in the central strait, and the cross-strait asymmetry (greater amplitudes in the west and smaller in the east) of the anti-nodal band. The superposition of Poincaré modes can further improve the model result in that the cross-strait asymmetry can be better reproduced. In order to explore the formation mechanism of the northward propagating wave in the TS three experiments are carried out, including the deep basin south of the strait. The results show that the southward incident wave can be reflected to form a northward wave by the abruptly deepened topography south of the strait, but the reflected wave is slightly weaker than the northward wave obtained from above analytical solution, in which the southern open boundary condition is specified with observations. The forcing at the Luzon Strait can strengthen the northward Kelvin wave in the TS, and thus is of secondary importance to the M2 tide in the TS.

scholarly journals Dynamics and Energetics of Trapped Diurnal Internal Kelvin Waves around a Midlatitude Island

2017 ◽  
Vol 47 (10) ◽  
pp. 2479-2498 ◽  
Author(s):  
Eiji Masunaga ◽  
Oliver B. Fringer ◽  
Yujiro Kitade ◽  
Hidekatsu Yamazaki ◽  
Scott M. Gallager
Keyword(s):  
Three Dimensional ◽  
Internal Tide ◽  
Kelvin Waves ◽  
Internal Tides ◽  
Navier Stokes ◽  
Kelvin Wave ◽  
Sagami Bay ◽  
Study Region ◽  
Topographic Slope ◽  
Terrain Following

AbstractThe generation of trapped and radiating internal tides around Izu‐Oshima Island located off Sagami Bay, Japan, is investigated using the three-dimensional Stanford Unstructured Nonhydrostatic Terrain-following Adaptive Navier–Stokes Simulator (SUNTANS) that is validated with observations of isotherm displacements in shallow water. The model is forced by barotropic tides, which generate strong baroclinic internal tides in the study region. Model results showed that when diurnal K1 barotropic tides dominate, resonance of a trapped internal Kelvin wave leads to large-amplitude internal tides in shallow waters on the coast. This resonance produces diurnal motions that are much stronger than the semidiurnal motions. The weaker, freely propagating, semidiurnal internal tides are generated on the western side of the island, where the M2 internal tide beam angle matches the topographic slope. The internal wave energy flux due to the diurnal internal tides is much higher than that of the semidiurnal tides in the study region. Although the diurnal internal tide energy is trapped, this study shows that steepening of the Kelvin waves produces high-frequency internal tides that radiate from the island, thus acting as a mechanism to extract energy from the diurnal motions.

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