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.

Energetics of Barotropic and Baroclinic Tides in the Monterey Bay Area

2012 ◽  
Vol 42 (2) ◽  
pp. 272-290 ◽  
Author(s):  
Dujuan Kang ◽  
Oliver Fringer
Keyword(s):  
Energy Flux ◽  
Three Dimensional ◽  
Internal Tide ◽  
Submarine Canyon ◽  
Tidal Energy ◽  
Energy Partitioning ◽  
Navier Stokes ◽  
Monterey Bay ◽  
Topographic Features ◽  
Bay Area

Abstract A detailed energy analysis of the barotropic and baroclinic M2 tides in the Monterey Bay area is performed. The authors first derive a theoretical framework for analyzing internal tide energetics based on the complete form of the barotropic and baroclinic energy equations, which include the full nonlinear and nonhydrostatic energy flux contributions as well as an improved evaluation of the available potential energy. This approach is implemented in the Stanford Unstructured Nonhydrostatic Terrain-Following Adaptive Navier–Stokes Simulator (SUNTANS). Results from three-dimensional, high-resolution SUNTANS simulations are analyzed to estimate the tidal energy partitioning among generation, radiation, and dissipation. A 200 km × 230 km domain including all typical topographic features in this region is used to represent the Monterey Bay area. Of the 152-MW energy lost from the barotropic tide, approximately 133 MW (88%) is converted into baroclinic energy through internal tide generation, and 42% (56 MW) of this baroclinic energy radiates away into the open ocean. The tidal energy partitioning depends greatly on the topographic features. The Davidson Seamount is most efficient at baroclinic energy generation and radiation, whereas the Monterey Submarine Canyon acts as an energy sink. Energy flux contributions from nonlinear and nonhydrostatic effects are also examined. In the Monterey Bay area, the nonlinear and nonhydrostatic contributions are quite small. Moreover, the authors investigate the character of internal tide generation and find that in the Monterey Bay area the generated baroclinic tides are mainly linear and in the form of internal tidal beams. Comparison of the modeled tidal conversion to previous theoretical estimates shows that they are consistent with one another.

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 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 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 An Analysis of Convectively Coupled Kelvin Waves in 20 WCRP CMIP3 Global Coupled Climate Models

2010 ◽  
Vol 23 (11) ◽  
pp. 3031-3056 ◽  
Author(s):  
Katherine H. Straub ◽  
Patrick T. Haertel ◽  
George N. Kiladis
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Three Dimensional ◽  
Kelvin Waves ◽  
Global Climate Models ◽  
Specific Humidity ◽  
Tropospheric Temperature ◽  
Wave Band ◽  
Kelvin Wave ◽  
Shallow Convection

Abstract Output from 20 coupled global climate models is analyzed to determine whether convectively coupled Kelvin waves exist in the models, and, if so, how their horizontal and vertical structures compare to observations. Model data are obtained from the World Climate Research Program’s (WCRP’s) Coupled Model Intercomparison Project phase 3 (CMIP3) multimodel dataset. Ten of the 20 models contain spectral peaks in precipitation in the Kelvin wave band, and, of these 10, only 5 contain wave activity distributions and three-dimensional wave structures that resemble the observations. Thus, the majority (75%) of the global climate models surveyed do not accurately represent convectively coupled Kelvin waves, one of the primary sources of submonthly zonally propagating variability in the tropics. The primary feature common to the five successful models is the convective parameterization. Three of the five models use the Tiedtke–Nordeng convective scheme, while the other two utilize the Pan and Randall scheme. The 15 models with less success at generating Kelvin waves predominantly contain convective schemes that are based on the concept of convective adjustment, although it appears that those schemes can be improved by the addition of convective “trigger” functions. Three-dimensional Kelvin wave structures in the five successful models resemble observations to a large degree, with vertically tilted temperature, specific humidity, and zonal wind anomalies. However, no model completely captures the observed signal, with most of the models being deficient in lower-tropospheric temperature and humidity signals near the location of maximum precipitation. These results suggest the need for improvements in the representations of shallow convection and convective downdrafts in global models.

scholarly journals Internal Tides in the Southwestern Atlantic off Brazil: Observations and Numerical Modeling

2007 ◽  
Vol 37 (6) ◽  
pp. 1512-1526 ◽  
Author(s):  
Adriene F. Pereira ◽  
Belmiro M. Castro
Keyword(s):  
Continental Shelf ◽  
Three Dimensional ◽  
Internal Tide ◽  
Equation Model ◽  
Shelf Break ◽  
Internal Tides ◽  
Southwestern Atlantic ◽  
Model Response ◽  
Southwestern Atlantic Ocean ◽  
Vertical Displacements

Abstract Data collected from moored instruments, deployed over the southeastern Brazilian continental shelf during the summer and winter months of 2001, show internal tide activity near the shelf break. To help to elucidate the observations, a fully three-dimensional nonlinear primitive equation model is applied to simulate the regional barotropic and baroclinic tides. Two semidiurnal (M2 and S2) and two diurnal (K1 and O1) tidal frequencies are considered. Tidal surface elevations are relatively small over the whole modeled area, reaching maximum values of about 0.40 m for M2 and 0.11 m for O1. Comparison between observed and computed tide elevation and Greenwich phase shows reasonable agreement. When the baroclinic response of the model is investigated, stratification is prescribed using summer and winter climatology data of potential density. In this case, the model response to summer and winter stratifications is very similar and internal tides are generated over the shelf break and slope, with vertical displacements up to 25 m, and seaward propagation. Modeled semidiurnal tidal ellipses agree well with winter and summer observations. Observed diurnal tidal ellipses in the middle of the continental shelf and close to the shelf break during summer show an intensification through the water column that could not be represented by the model. Estimates of the total baroclinic M2 offshore energy flux are about 3.5 and 0.5 MW considering winter and summer stratifications, respectively. Although these quantities are three orders of magnitude less than that estimated for regions known for intense internal tides, they refer to offshore fluxes computed for a very small section of the southeastern Brazilian shelf. This is the first published investigation into internal tides in the southwestern Atlantic Ocean off Brazil.

scholarly journals Accuracy assessment of global internal tide models using satellite altimetry

2020 ◽  
Author(s):  
Loren Carrere ◽  
Brian K. Arbic ◽  
Brian Dushaw ◽  
Gary D. Egbert ◽  
Svetlana Y. Erofeeva ◽  
...  
Keyword(s):  
Variance Reduction ◽  
Accuracy Assessment ◽  
Three Dimensional ◽  
Internal Tide ◽  
Detailed Comparison ◽  
Internal Tides ◽  
Global Ocean ◽  
Ocean Tide ◽  
Small Scale ◽  
Ocean Topography

Abstract. In order to access the targeted ocean signal, altimeter measurements are corrected for several geophysical parameters among which the ocean tide correction is one of the most critical, but the internal tide signature at the surface are not yet corrected globally. Internal tides can have a signature of several cm at the surface with wavelengths about 50–250 km for the first mode and even smaller scales for higher order modes. The goals of the upcoming Surface Water Ocean Topography (SWOT) mission and other high-resolution ocean measurements make the correction of these small scale signals a challenge, as the separation of all tidal variability from other oceanic signals becomes mandatory. In this context, several scientific teams are working on the development of new internal tide models, taking advantage of the very long altimeter time series now available, which represent an unprecedented and valuable global ocean database. The internal tide models presented here focus on the coherent internal tide signal and they are of three types: empirical models based upon analysis of existing altimeter missions, an assimilative model, and a three-dimensional hydrodynamic model. A detailed comparison and validation of these internal tide models is proposed using existing satellite altimeter databases. The analysis focuses on the four main tidal constituents M2, K1, O1 and S2. The validation process is based on a statistical analysis of multi-mission altimetry including Jason-2 and Cryosphere Satellite-2 data, taking advantage of the long-term altimeter databases available. The results show a significant altimeter variance reduction when using internal tide corrections on all ocean regions where internal tides are generating/propagating. A complementary spectral analysis also gives some estimation of the performance of each model as a function of wavelength, and some insight into the residual non-stationary part of internal tides in the different regions of interest.

scholarly journals Tidal Conversion and Dissipation at Steep Topography in a Channel Poleward of the Critical Latitude

2019 ◽  
Vol 49 (5) ◽  
pp. 1269-1291 ◽  
Author(s):  
Kenneth G. Hughes ◽  
Jody M. Klymak
Keyword(s):  
Three Dimensional ◽  
Tidal Energy ◽  
Kelvin Waves ◽  
Internal Tides ◽  
The Arctic ◽  
Energy Budgets ◽  
Dimensional System ◽  
Deep Layers ◽  
The Stability ◽  
Critical Latitude

Abstract In high-latitude fjords and channels in the Canadian Arctic Archipelago, walls support radiating internal tides as Kelvin waves. Such waves allow for significant barotropic to baroclinic tidal energy conversion, which is otherwise small or negligible when poleward of the critical latitude. This fundamentally three-dimensional system of a subinertial channel is investigated with a suite of numerical simulations in rectangular channels of varying width featuring idealized, isolated ridges. Even in channels as wide as 5 times the internal Rossby radius, tidal conversion can remain as high as predicted by an equivalent two-dimensional, nonrotating system. Curves of tidal conversion as a function of channel width, however, do not vary monotonically. Instead, they display peaks and nulls owing to interference between the Kelvin waves along the wall and similar waves that propagate along the ridge flanks, the wavelengths of which can be estimated from linear theory to guide prediction. Because the wavelengths are comparable to width scales of Arctic channels and fjords, the interference will play a first-order role in tidal energy budgets and may consequently influence the stability of glaciers, the ventilation of deep layers, the locations of sediment deposition, and the fate of freshwater exiting the Arctic Ocean.

scholarly journals Multi-scale phenomena of rotation-modified mode-2 internal waves

2018 ◽  
Vol 25 (1) ◽  
pp. 217-231 ◽  
Author(s):  
David Deepwell ◽  
Marek Stastna ◽  
Aaron Coutino
Keyword(s):  
Three Dimensional ◽  
Side Wall ◽  
Kelvin Waves ◽  
Kelvin Wave ◽  
Rotation Rates ◽  
Multi Scale ◽  
Mode 2 ◽  
Schmidt Numbers ◽  
Poincare Waves ◽  
The Right

Abstract. We present high-resolution, three-dimensional simulations of rotation-modified mode-2 internal solitary waves at various rotation rates and Schmidt numbers. Rotation is seen to change the internal solitary-like waves observed in the absence of rotation into a leading Kelvin wave followed by Poincaré waves. Mass and energy is found to be advected towards the right-most side wall (for a Northern Hemisphere rotation), leading to increased amplitude of the leading Kelvin wave and the formation of Kelvin–Helmholtz (K–H) instabilities on the upper and lower edges of the deformed pycnocline. These fundamentally three-dimensional instabilities are localized within a region near the side wall and intensify in vigour with increasing rotation rate. Secondary Kelvin waves form further behind the wave from either resonance with radiating Poincaré waves or the remnants of the K–H instability. The first of these mechanisms is in accord with published work on mode-1 Kelvin waves; the second is, to the best of our knowledge, novel to the present study. Both types of secondary Kelvin waves form on the same side of the channel as the leading Kelvin wave. Comparisons of equivalent cases with different Schmidt numbers indicate that while adopting a numerically advantageous low Schmidt number results in the correct general characteristics of the Kelvin waves, excessive diffusion of the pycnocline and various density features precludes accurate representation of both the trailing Poincaré wave field and the intensity and duration of the Kelvin–Helmholtz instabilities.

scholarly journals Decomposition of the Multimodal Multidirectional M2 Internal Tide Field

2019 ◽  
Vol 36 (6) ◽  
pp. 1157-1173 ◽  
Author(s):  
Zhongxiang Zhao ◽  
Jinbo Wang ◽  
Dimitris Menemenlis ◽  
Lee-Lueng Fu ◽  
Shuiming Chen ◽  
...  
Keyword(s):  
Continental Slope ◽  
Internal Tide ◽  
Internal Tides ◽  
Global Ocean ◽  
Decomposition Technique ◽  
Study Region ◽  
Tidal Constituents ◽  
Mode 3 ◽  
Baroclinic Modes ◽  
Arbitrary Propagation

AbstractThe M2 internal tide field contains waves of various baroclinic modes and various horizontal propagation directions. This paper presents a technique for decomposing the sea surface height (SSH) field of the multimodal multidirectional internal tide. The technique consists of two steps: first, different baroclinic modes are decomposed by two-dimensional (2D) spatial filtering, utilizing their different horizontal wavelengths; second, multidirectional waves in each mode are decomposed by 2D plane wave analysis. The decomposition technique is demonstrated using the M2 internal tide field simulated by the MITgcm. This paper focuses on a region lying off the U.S. West Coast ranging 20°–50°N, 220°–245°E. The lowest three baroclinic modes are separately resolved from the internal tide field; each mode is further decomposed into five waves of arbitrary propagation directions in the horizontal. The decomposed fields yield unprecedented details on the internal tide’s generation and propagation, which cannot be observed in the harmonically fitted field. The results reveal that the mode-1 M2 internal tide in the study region is dominantly from the Hawaiian Ridge to the west but also generated locally at the Mendocino Ridge and continental slope. The mode-2 and mode-3 M2 internal tides are generated at isolated seamounts, as well as at the Mendocino Ridge and continental slope. The Mendocino Ridge radiates both southbound and northbound M2 internal tides for all three modes. Their propagation distances decrease with increasing mode number: mode-1 waves can travel over 2000 km, while mode-3 waves can only be tracked for 300 km. The decomposition technique may be extended to other tidal constituents and to the global ocean.

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