The Shaping of Continental Slopes by Internal Tides

Science ◽  
2002 ◽  
Vol 296 (5568) ◽  
pp. 724-727 ◽  
Author(s):  
D. A. Cacchione
Keyword(s):  
Internal Tides ◽  
Continental Slopes

Spatial-temporal variability of M2 internal tides modulated by the Kuroshio currents and mesoscale eddies northeast of Taiwan

2020 ◽  
Author(s):  
Hang Chang ◽  
Yahao Liu
Keyword(s):  
High Resolution ◽  
Temporal Variability ◽  
Internal Tide ◽  
Mesoscale Eddies ◽  
Vertical Displacement ◽  
Internal Tides ◽  
Time Varying ◽  
Energy Beam ◽  
Continental Slopes ◽  
The Kuroshio

<p>The spatial-temporal variability and energetics of M2 internal tides during their generation and propagation through the Kuroshio flows and robust eddies northeast of Taiwan are investigated using a high-resolution numerical model. The corrugated continental slopes, particularly the I-Lan Ridge and Mien-Hua Canyon, are identified as the energetic sources of M2 internal tides. The M2 internal tide generation is influenced by the horizontally varying and zonally tilting stratification associated with the Kuroshio currents and mesoscale eddies. In this situation, the magnitude of conversion rate and energy beam exhibit highly temporal variability. An energetic along-slope tidal beam from the I-Lan Ridge radiates southward against the northward Kuroshio flows, causing strong vertical displacement. Complex background currents lead to the time-varying inhomogeneous diapycnal mixing induced by internal tide dissipation.</p>

scholarly journals On barotropic and baroclinic tides over an arbitrary sloping topography

1996 ◽  
Vol 14 (9) ◽  
pp. 961-975 ◽  
Author(s):  
J. Y. Le Tareau ◽  
R. Maze
Keyword(s):  
Continental Slope ◽  
Arbitrary Shape ◽  
Numerical Procedure ◽  
Internal Tides ◽  
Theoretical Concepts ◽  
Barotropic Tide ◽  
Continental Slopes ◽  
Harmonic Components ◽  
Sloping Bottom ◽  
Sloping Topography

Abstract. Some theoretical concepts about the frictionless dynamics of propagation of the barotropic tide over two-dimensional continental slopes of arbitrary shape are developed. A numerical procedure which generalizes the exact solution obtained over a rectilinear sloping topography is given. This technique can be applied to compute the harmonic components of the barotropic tide everywhere over sloping bottom contours of any shape. It permits in particular the avoidance of discontinuities at the boundaries of rectilinear-continental-slope profiles. The barotropic tidal results are used afterwards to calculate the barotropic forcing for the generation of internal tides. Numerical experiments are performed to study the interaction between the tide and some typical sloping topographies. A three-layered model is used for this purpose. Results are compared with those previously obtained over a rectilinear continental slope.

Internal Bores and Breaking Internal Tides on the Oregon Continental Slope

2013 ◽  
Vol 43 (1) ◽  
pp. 120-139 ◽  
Author(s):  
Kim I. Martini ◽  
Matthew H. Alford ◽  
Eric Kunze ◽  
Samuel M. Kelly ◽  
Jonathan D. Nash
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Continental Slope ◽  
Internal Tide ◽  
Internal Tides ◽  
Dissipation Rates ◽  
Continental Slopes ◽  
Internal Bores ◽  
Acoustic Doppler Current Profilers ◽  
Temperature Time

Abstract Observations of breaking internal tides on the Oregon continental slope during a 40-day deployment of 5 moorings along 43°12′N are presented. Remotely generated internal tides shoal onto the slope, steepen, break, and form turbulent bores that propagate upslope independently of the internal tide. A high-resolution snapshot of a single bore is captured from lowered acoustic Doppler current profilers (LADCP)/CTD profiles in a 25-h time series at 1200 m. The bore is cold, salty, over 100 m tall, and has a turbulent head where instantaneous dissipation rates are enhanced (ε > 10−6 W kg−1) and sediment is resuspended. At the two deepest slope moorings (1452 and 1780 m), similar borelike phenomena are observed in near-bottom high-resolution temperature time series. Mean dissipation rates and diapycnal diffusivities increase by a factor of 2 when bores are present ( W kg−1 and m s−1) and observed internal tides are energetic enough to drive these enhanced dissipation rates. Globally, the authors estimate an average of 1.3 kW m−1 of internal tide energy flux is directed onto continental slopes. On the Oregon slope, internal tide fluxes are smaller, suggesting that it is a relatively weak internal tide sink. Mixing associated with the breaking of internal tides is therefore likely to be larger on other continental slopes.

scholarly journals A Coupled Model for Laplace's Tidal Equations in a Fluid with One Horizontal Dimension and Variable Depth

2013 ◽  
Vol 43 (8) ◽  
pp. 1780-1797 ◽  
Author(s):  
Samuel M. Kelly ◽  
Nicole L. Jones ◽  
Jonathan D. Nash
Keyword(s):  
Energy Flux ◽  
Internal Tide ◽  
Surface Displacement ◽  
Tidal Energy ◽  
Internal Tides ◽  
Energy Fluxes ◽  
Flux Divergence ◽  
Flat Bottom ◽  
Horizontal Dimension ◽  
Continental Slopes

Abstract Tide–topography interactions dominate the transfer of tidal energy from large to small scales. At present, it is poorly understood how low-mode internal tides reflect and scatter along the continental margins. Here, the coupling equations for linear tides model (CELT) are derived to determine the independent modal solutions to Laplace's Tidal Equations (LTE) over stepwise topography in one horizontal dimension. CELT is (i) applicable to arbitrary one-dimensional topography and realistic stratification without requiring numerically expensive simulations and (ii) formulated to quantify scattering because it implicitly separates incident and reflected waves. Energy fluxes and horizontal velocities obtained using CELT are shown to converge to analytical solutions, indicating that “flat bottom” modes, which evolve according to LTE, are also relevant in describing tides over sloping topography. The theoretical framework presented can then be used to quantify simultaneous incident and reflected energy fluxes in numerical simulations and observations of tidal flows that vary in one horizontal dimension. Thus, CELT can be used to diagnose internal-tide scattering on continental slopes. Here, semidiurnal mode-1 scattering is simulated on the Australian northwest, Brazil, and Oregon continental slopes. Energy-flux divergence and directional energy fluxes computed using CELT are shown to agree with results from a finite-volume model that is significantly more numerically expensive. Last, CELT is used to examine the dynamics of two-way surface–internal-tide coupling. Semidiurnal mode-1 internal tides are found to transmit about 5% of their incident energy flux to the surface tide where they impact the continental slope. It is hypothesized that this feedback may decrease the coherence of sea surface displacement on continental shelves.

The generation of internal tides over steep continental slopes

1974 ◽  
Vol 277 (1263) ◽  
pp. 27-58 ◽  
Keyword(s):  
Energy Flux ◽  
Bottom Topography ◽  
Numerical Procedure ◽  
Internal Tides ◽  
Shear Instability ◽  
Radius Of Curvature ◽  
Energy Propagation ◽  
Wide Range ◽  
Concave Corner ◽  
Continental Slopes

A numerical procedure is presented for the calculation of internal tides generated by the interaction of surface tide with bottom topography which is tangent to the direction of internal tidal energy propagation at some depth. This procedure, together with that of Baines (1973), permits the calculation of internal tides generated by (virtually) arbitrary topography with horizontal scale greater than 1 km, and a wide range of realistic density stratifications. The procedure is applied to continental slopes with simple linear and quartercircle profiles, and constant stratification. For these cases, the largest internal tidal velocities and energy densities occur in regions around characteristics emanating from the tangential corner point; on the shallow shelf side the energy flux is a maximum in this region, but on the deep side it is a minimum and is distributed more evenly with depth. The total energy flux is greater than the maximum for flat-bump topography of comparable height by a factor of order 2-3. It increases nearly exponentially with height but is less sensitive to shape provided the slope is greater than critical, and is greater on the deep than on the shallow side by a factor of order 10. Calculations for more realistic density stratifications yield similar results. The procedure is also applied to a real continental slope for which observations have been made by Wunsch & Hendry (1972), with stratification representing summer and winter conditions. The velocity fields and associated energy fluxes differ significantly from those of simple geometries, and are also sensitive to the seasonal density changes in the upper 50 m. It is suggested that internal tidal generation will give rise to two mixing processes, one associated with the boundary layer near the tangent point and the other with shear instability in the velocity profile. Instability of the theoretical profiles according to the Richardson number criterion may be readily achieved in oceanic conditions. The reflexion of an internal wave from a concave corner is discussed in an appendix, where it is shown that no singularities occur unless the radius of curvature is very large.

Controls on the evolution of submarine canyons in steep continental slopes: geomorphological insights from Palar Basin, southeastern margin of India

2021 ◽  
Vol 41 (1) ◽  
Author(s):  
S. Susanth ◽  
P. John Kurian ◽  
C. M. Bijesh ◽  
D. Twinkle ◽  
Abhishek Tyagi ◽  
...  
Keyword(s):  
Submarine Canyons ◽  
Continental Slopes ◽  
Southeastern Margin ◽  
Palar Basin

scholarly journals Satellite Investigation of Semidiurnal Internal Tides in the Sulu-Sulawesi Seas

2021 ◽  
Vol 13 (13) ◽  
pp. 2530
Author(s):  
Xiaoyu Zhao ◽  
Zhenhua Xu ◽  
Ming Feng ◽  
Qun Li ◽  
Peiwen Zhang ◽  
...  
Keyword(s):  
Interference Pattern ◽  
Energy Flux ◽  
Internal Tide ◽  
Tidal Energy ◽  
Internal Tides ◽  
Altimeter Data ◽  
Band Pass Filter ◽  
Pass Filter ◽  
Sulu Sea ◽  
Tidal Energy Flux

The mode-1 semidiurnal internal tides that emanate from multiple sources in the Sulu-Sulawesi Seas are investigated using multi-satellite altimeter data from 1993–2020. A practical plane-wave analysis method is used to separately extract multiple coherent internal tides, with the nontidal noise in the internal tide field further removed by a two-dimensional (2-D) spatial band-pass filter. The complex radiation pathways and interference patterns of the internal tides are revealed, showing a spatial contrast between the Sulu Sea and the Sulawesi Sea. The mode-1 semidiurnal internal tides in the Sulawesi Sea are effectively generated from both the Sulu and Sangihe Island chains, forming a spatially inhomogeneous interference pattern in the deep basin. A cylindrical internal tidal wave pattern from the Sibutu passage is confirmed for the first time, which modulates the interference pattern. The interference field can be reproduced by a line source model. A weak reflected internal tidal beam off the Sulawesi slope is revealed. In contrast, the Sulu Island chain is the sole energetic internal tide source in the Sulu Sea, thus featuring a relatively consistent wave and energy flux field in the basin. These energetic semidiurnal internal tidal beams contribute to the frequent occurrence of internal solitary waves (ISWs) in the study area. On the basis of the 28-year consistent satellite measurements, the northward semidiurnal tidal energy flux from the Sulu Island chain is 0.46 GW, about 25% of the southward energy flux. For M2, the altimetric estimated energy fluxes from the Sulu Island chain are about 80% of those from numerical simulations. The total semidiurnal tidal energy flux from the Sulu and Sangihe Island chains into the Sulawesi Sea is about 2.7 GW.

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