scholarly journals Summertime M2 Internal Tides in the Northern Yellow Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Fan Lin ◽  
Lars Asplin ◽  
Hao Wei
Keyword(s):  
Yellow Sea ◽  
Current Model ◽  
Internal Tide ◽  
Horizontal Resolution ◽  
Ocean Model ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Regional Ocean Model System ◽  
Strong Current ◽  
Northern Yellow Sea

The summertime M2 internal tide in the northern Yellow Sea is investigated with moored current meter observations and numerical current model results. The hydrodynamic model, which is implemented from the Regional Ocean Model System (ROMS) with 1 km horizontal resolution, is capable of resolving the internal tidal dynamics and the results are validated in a comparison with observations. The vertical pattern of a mode-1, semi-diurnal internal tide is clearly captured by the moored ADCP as well as in the simulation results. Spectral analysis of the current results shows that the M2 internal tide is dominant in the northern Yellow Sea. Analysis of the major M2 internal tide energetics demonstrated a complex spatial pattern. The tidal mixing front along the Korean coast and on the northern shelf provided proper conditions for the generation and propagation of the internal tides. Near the Changshan islands, the M2 internal tide is mainly generated near the local topography anomalies with relatively strong current magnitude, equal to about 30% of the barotropic component, thus modifying the local current field. These local internal tides are short-lived phenomena rapidly being dissipated along the propagation pathway, restricting their influence within a few kilometers around the islands.

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>

The dissipation of the internal tide inferred from a global ocean model, altimetry, and in-situ observations

2020 ◽  
Author(s):  
Maarten Buijsman ◽  
Harpreet Kaur ◽  
Zhongxiang Zhao ◽  
Amy Waterhouse ◽  
Caitlin Whalen
Keyword(s):  
Correction Factor ◽  
Internal Tide ◽  
Horizontal Resolution ◽  
Ocean Model ◽  
Internal Tides ◽  
Global Ocean ◽  
Flux Divergence ◽  
Data Set ◽  
Tidal Dissipation ◽  
Dissipation Rates

<p>In this presentation we combine several model and observational data sets to better understand the dissipation of the diurnal and semidiurnal internal tide in the global ocean, which is relevant for maintaining the global overturning circulation. We compute depth-integrated internal tide dissipation rates from a realistically-forced global HYbrid Coordinate Ocean Model (HYCOM) simulation with a horizontal resolution of 4 km (1/25 degrees) and 41 layers. We also compute dissipation rates from altimetry in two ways: 1) from the low-mode flux divergence away from topography and 2) by fitting exponential decay curves along low-mode internal tide beams. The internal-tide sea-surface height amplitude is computed with a least-squares harmonic analysis over a 20+ year altimetry data set. Hence, the altimetry-inferred dissipation rates both reflect the tidal dissipation and the energy scattered from the stationary to the nonstationary internal tide. To account for the dissipation of the nonstationary tide, we apply a spatially-varying correction factor to the stationary dissipation inferred from altimetry.  This correction factor is computed from a global 8-km HYCOM simulation with a duration of 6 years, from which the stationary and nonstationary internal tides can be easily isolated. We compare the simulated and the corrected altimetry-inferred dissipation rates with dissipation rates from finescale and microstructure observations. Preliminary results show that the simulated dissipation is up to a factor of two larger than the depth-integrated dissipation rates inferred from finescale methods, but smaller than the dissipation rates from microstructure.</p>

Internal-Wave-Driven Mixing: Global Geography and Budgets

2017 ◽  
Vol 47 (6) ◽  
pp. 1325-1345 ◽  
Author(s):  
Eric Kunze
Keyword(s):  
Internal Wave ◽  
Internal Tide ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Linear Wave ◽  
Power Sources ◽  
The North ◽  
Dissipation Rates ◽  
Thickness Variability ◽  
Significant Pathway

AbstractInternal-wave-driven dissipation rates ε and diapycnal diffusivities K are inferred globally using a finescale parameterization based on vertical strain applied to ~30 000 hydrographic casts. Global dissipations are 2.0 ± 0.6 TW, consistent with internal wave power sources of 2.1 ± 0.7 TW from tides and wind. Vertically integrated dissipation rates vary by three to four orders of magnitude with elevated values over abrupt topography in the western Indian and Pacific as well as midocean slow spreading ridges, consistent with internal tide sources. But dependence on bottom forcing is much weaker than linear wave generation theory, pointing to horizontal dispersion by internal waves and relatively little local dissipation when forcing is strong. Stratified turbulent bottom boundary layer thickness variability is not consistent with OGCM parameterizations of tidal mixing. Average diffusivities K = (0.3–0.4) × 10−4 m2 s−1 depend only weakly on depth, indicating that ε = KN2/γ scales as N2 such that the bulk of the dissipation is in the pycnocline and less than 0.08-TW dissipation below 2000-m depth. Average diffusivities K approach 10−4 m2 s−1 in the bottom 500 meters above bottom (mab) in height above bottom coordinates with a 2000-m e-folding scale. Average dissipation rates ε are 10−9 W kg−1 within 500 mab then diminish to background deep values of 0.15 × 10−9 W kg−1 by 1000 mab. No incontrovertible support is found for high dissipation rates in Antarctic Circumpolar Currents or parametric subharmonic instability being a significant pathway to elevated dissipation rates for semidiurnal or diurnal internal tides equatorward of 28° and 14° latitudes, respectively, although elevated K is found about 30° latitude in the North and South Pacific.

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.

Scattering of internal tide energy to super-tidal frequencies in global HYCOM 

2021 ◽  
Author(s):  
Miguel Solano ◽  
Maarten Buijsman
Keyword(s):  
Internal Tide ◽  
Tidal Energy ◽  
Horizontal Resolution ◽  
Internal Tides ◽  
Numerical Dispersion ◽  
Global Ocean ◽  
Wave Interactions ◽  
Continental Shelves ◽  
Lee Wave ◽  
Ocean Models

<p>Energy decay in realistically forced global ocean models has been mostly studied in the diurnal and semi-diurnal tidal bands and it is unclear how much of the tidal energy in these bands is scattered to higher frequencies. Global ocean models and satellite altimetry have shown that low-mode internal tides can propagate thousands of kilometers from their generation sites before being dissipated in the ocean interior but their pathway to dissipation is obscured due to lee-wave breaking at generation, wave-wave interactions, topographic scattering, shearing instabilities and shoaling on continental shelves. Internal tides from some generation sites, such as the Amazon shelf and the Nicobar and Andaman island chain, have large amounts of energy resulting in a steepening of the internal waves into solitary wave trains due to non-hydrostatic dispersion. In HYCOM, a hydrostatic model, this process is partially simulated by numerical dispersion. However, it is yet unknown how the dissipation of internal tides is affected by the numerical dispersion in hydrostatic models. In this study we use the method of vertical modes and rotary spectra to quantify the scattering of internal tides to higher-frequencies and analyze the dissipation processes in global HYCOM simulations with 4-km horizontal resolution.</p>

Interaction between Upwelling and Internal Tide in the East Qiongzhou Strait Areas

2015 ◽  
Vol 1092-1093 ◽  
pp. 1160-1164 ◽  
Author(s):  
Peng Bai ◽  
Pei Liang Li ◽  
Yan Zhen Gu ◽  
Ke Jian Wu
Keyword(s):  
Internal Tide ◽  
Hainan Island ◽  
Ocean Model ◽  
Preferred Direction ◽  
Regional Ocean Model System ◽  
Qiongzhou Strait ◽  
Good Reproduction ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Upwelling Event

An upwelling event that occurred off the east Hainan Island coast in summer 2010 is captured by processing the Moderate Resolution Imaging Spectroradiometer (MODIS) sea surface temperature (SST) data. High resolution Regional Ocean Model System (ROMS) is employed to study this upwelling event, and is proved to provide good reproduction of this upwelling event by comparing ROMS SST with MODIS SST. It is detected that internal tide generated and interacted with the upwelling in the east Qiongzhou Strait areas. The upwelling and the internal tide modulated each other: the uplift of the isopycnal due to the fluctuation of the internal tide enhanced the upwelling; in another aspect, the upwelling changed the background stratification which is sufficient to control the amount of barotropic-to-baroclinic energy conversion and the preferred direction of baroclinic energy flux [21].

scholarly journals A Fine Grid Tide-Wave-Ocean Circulation Coupled Model for the Yellow Sea: Comparison of Turbulence Closure Schemes in Reproducing Temperature Distributions

2021 ◽  
Vol 9 (12) ◽  
pp. 1460
Author(s):  
Youngjin Choi ◽  
Youngmin Park ◽  
Min-Bum Choi ◽  
Kyung Tae Jung ◽  
Kyeong Ok Kim
Keyword(s):  
Ocean Circulation ◽  
Yellow Sea ◽  
Horizontal Resolution ◽  
Turbulence Closure ◽  
Tidal Mixing ◽  
The Yellow Sea ◽  
Western Slope ◽  
Fine Grid ◽  
Tidal Mixing Front ◽  
Mean Square Errors

The performance of three turbulence closure schemes (TCSs), the generic length scale scheme (GLS), the Mellor–Yamada 2.5 scheme (MY2.5) and the K-profile parameterization scheme (KPP), embedded in the ocean model ROMS, was compared with attention to the reproduction of summertime temperature distribution in the Yellow Sea. The ROMS model has a horizontal resolution of 1/30° and 30 vertical sigma layers. For model validation, root mean square errors were checked, comparing model results with wave and temperature buoy data as well as tidal station data supplied by various organizations within the Republic of Korea. Computed temperature and vertical temperature diffusion coefficients were mainly compared along Lines A (36° N) and B (125° E) crossing the central Yellow Sea, Lines C (32° N) and E (34° N) passing over the Yangtze Bank and Line D off the Taean Peninsula. Calculations showed that GLS and MY2.5 produced vertical mixing stronger than KPP in both the surface and bottom layers, but the overall results were reasonably close to each other. The lack of observational data was a hindrance in comparing the detailed performance between the TCSs. However, it was noted that the simulation capability of cold patches in the tidal mixing front can be useful in identifying the better performing turbulence closure scheme. GLS and MY2.5 clearly produced the cold patch located near the western end of Line E (122° E–122.3° E), while KPP hardly produced its presence. Similar results were obtained along Line D but with a less pronounced tidal mixing front. Along Line C, GLS and MY2.5 produced a cold patch on the western slope of the Yellow Sea, the presence of which had never been reported. Additional measurements near 125° E–126° E of Line C and along the channel off the Taean Peninsula (Line D) are recommended to ensure the relative performance superiority between the TCSs.

scholarly journals Tidal effects on ichthyoplankton aggregation and dispersion in the Southern Gulf of Mexico

2013 ◽  
Vol 61 (4) ◽  
pp. 231-241 ◽  
Author(s):  
María Adela Monreal Gómez ◽  
David Alberto Salas de León ◽  
Cesar Flores Coto ◽  
Fernando Flores Hernández ◽  
David Salas Monreal ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Single Point ◽  
Internal Tide ◽  
Ocean Model ◽  
Hydraulic Control ◽  
Barotropic Tide ◽  
Regional Ocean Model System ◽  
Southern Gulf Of Mexico ◽  
Regional Ocean Model

The role of vertical barotropic and baroclinic tidal forcing in the aggregation and dispersion of ichthyoplankton in the Southern Gulf of Mexico was analyzed in this study. Samplings of ichthyoplankton and the determination of hydrographic parameters were performed during September 1992 at a single point of 180 m depth, near the shelf break (19º32'N - 92º38.5'W). A 24 h CTD yo-yoing casting and biological samples were taken every 2 h and these measurements were combined with water velocity and density simulations from the Regional Ocean Model System (ROMS). One thermocline and two haloclines were depicted. The Froude number increased with a 2 h lag with respect to the maximal barotropic tide, suggesting the existence of a baroclinic tide. Aggregation and dispersion of the ichthyoplankton showed vertical oscillations in the abundance and the numbers of taxa and larvae with a 5 h lag with respect to the maximal barotropic tide and were in phase with the thermocline oscillation. The vertical oscillation was attributed to a hydraulic control forced by the internal tide.

scholarly journals Climatic Impacts of Parameterized Local and Remote Tidal Mixing

2016 ◽  
Vol 29 (10) ◽  
pp. 3473-3500 ◽  
Author(s):  
Angélique Melet ◽  
Sonya Legg ◽  
Robert Hallberg
Keyword(s):  
Turbulent Mixing ◽  
Water Mass ◽  
Internal Tide ◽  
Meridional Overturning Circulation ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Primary Role ◽  
Ocean Heat Uptake ◽  
Meridional Overturning ◽  
The Impact

Abstract Turbulent mixing driven by breaking internal tides plays a primary role in the meridional overturning and oceanic heat budget. Most current climate models explicitly parameterize only the local dissipation of internal tides at the generation sites, representing the remote dissipation of low-mode internal tides that propagate away through a uniform background diffusivity. In this study, a simple energetically consistent parameterization of the low-mode internal-tide dissipation is derived and implemented in the Geophysical Fluid Dynamics Laboratory Earth System Model with GOLD component (GFDL-ESM2G). The impact of remote and local internal-tide dissipation on the ocean state is examined using a series of simulations with the same total amount of energy input for mixing, but with different scalings of the vertical profile of dissipation with the stratification and with different idealized scenarios for the distribution of the low-mode internal-tide energy dissipation: uniformly over ocean basins, continental slopes, or continental shelves. In these idealized scenarios, the ocean state, including the meridional overturning circulation, ocean ventilation, main thermocline thickness, and ocean heat uptake, is particularly sensitive to the vertical distribution of mixing by breaking low-mode internal tides. Less sensitivity is found to the horizontal distribution of mixing, provided that distribution is in the open ocean. Mixing on coastal shelves only impacts the large-scale circulation and water mass properties where it modifies water masses originating on shelves. More complete descriptions of the distribution of the remote part of internal-tide-driven mixing, particularly in the vertical and relative to water mass formation regions, are therefore required to fully parameterize ocean turbulent mixing.

scholarly journals A practical scheme to introduce explicit tidal forcing into an OGCM

Ocean Science ◽  
2013 ◽  
Vol 9 (6) ◽  
pp. 1089-1108 ◽  
Author(s):  
K. Sakamoto ◽  
H. Tsujino ◽  
H. Nakano ◽  
M. Hirabara ◽  
G. Yamanaka
Keyword(s):  
General Circulation ◽  
Mean Squared Error ◽  
Nonlinear Effects ◽  
General Circulation Models ◽  
Ocean Model ◽  
Tidal Currents ◽  
Internal Tides ◽  
Tidal Mixing ◽  
Tidal Forcing ◽  
Practical Scheme

Abstract. A practical scheme is proposed to explicitly introduce tides into ocean general circulation models (OGCM). In this scheme, barotropic linear response to the tidal forcing is calculated by the time differential equations modified for ocean tides, instead of the original barotropic equations of an OGCM. This allows for the usage of various parameterizations specified for tides, such as the self-attraction/loading (SAL) effect and energy dissipation due to internal tides, without unintentional violation of the original dynamical balances in an OGCM. Meanwhile, secondary nonlinear effects of tides, e.g., excitation of internal tides and advection by tidal currents, are fully represented within the framework of the original OGCM equations. That is, this scheme drives the OGCM by the barotropic linear tidal currents which are predicted progressively by a tuned tide model, instead of the equilibrium tide potential, without large additional numerical costs. We incorporated this scheme into Meteorological Research Institute Community Ocean Model and executed test experiments with a low-resolution global model. The results showed that the model can simulate both the non-tidal circulations and the tidal motion simultaneously. Owing to the usage of tidal parameterizations such as a SAL term, a root-mean-squared error in the tidal heights is found to be as small as 10.0 cm, which is comparable to that of elaborately tuned tide models. In addition, analysis of the speed and energy of the barotropic tidal currents is found to be consistent with that of past tide studies. The model also showed active excitement of internal tides and tidal mixing. In the future, the impacts of internal tides and tidal mixing should be examined using a model with a finer resolution, since explicit and precise introduction of tides into an OGCM is a significant step toward the improvement of ocean models.

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