scholarly journals Current and Density Observations of Packets of Nonlinear Internal Waves on the Outer New Jersey Shelf

2011 ◽  
Vol 41 (5) ◽  
pp. 994-1008 ◽  
Author(s):  
W. J. Teague ◽  
H. W. Wijesekera ◽  
W. E. Avera ◽  
Z. R. Hallock
Keyword(s):  
New Jersey ◽  
Internal Waves ◽  
Propagation Speed ◽  
Mooring Line ◽  
Outer Continental Shelf ◽  
Density Profiles ◽  
Nonlinear Internal Waves ◽  
Multiple Phase ◽  
The Waves ◽  
Acoustic Doppler Current Profilers

Abstract Closely spaced observations of nonlinear internal waves (NLIWs) were made on the outer continental shelf off New Jersey in June 2009. Nearly full water column measurements of current velocity were made with four acoustic Doppler current profilers (ADCPs) that were moored about 5 km apart on the bottom along a line approximately normal to the bathymetry between water depths of 67 and 92 m. Density profiles were obtained from two vertical strings of temperature and conductivity sensors that were deployed near each of the interior ADCP moorings. In addition, a towed ScanFish provided profiles and fixed-level records of temperature and salinity through several NLIW packets near the moorings. Several case studies were selected to describe the propagation of the NLIWs. One to three solitary waves of depression were observed in five selected packets. There were also occurrences of multiple-phase dispersive wave packets. The average propagation speed corrected for advection of the observed waves was 0.51 ± 0.09 m s−1. The waves were directed primarily shoreward (~northwestward) along the mooring line with average wavelengths and periods of about 300 m and 10 min, respectively. Wave amplitudes and energies decreased with decreasing water depth. The observed wave parameters can be locally described by a two-layer Korteweg–de Vries (KdV) model, except for the decreasing amplitudes, which may be due to shear-induced dissipation and/or bottom drag. The various complementary observations utilized in this study present a unique description of NLIWs.

Propagation and transformation of nonlinear internal waves of tidal origin observed in the northeastern East China Sea

2020 ◽  
Author(s):  
Seung-Woo Lee ◽  
SungHyun Nam
Keyword(s):  
East China Sea ◽  
Internal Waves ◽  
Bottom Topography ◽  
Wave Interaction ◽  
Propagation Speed ◽  
East China ◽  
Modal Interactions ◽  
Nonlinear Internal Waves ◽  
China Sea ◽  
Mode 2

<p>Oceanic nonlinear internal waves (NLIWs) play an important role in regional circulation, biogeochemistry, energetics, vertical mixing, and underwater acoustics, causing hazards to marine engineering and submarine navigation. Mainly generated by the interaction of the barotropic tides with the bottom topography, they propagate and transform due to wave-wave interaction process. Here, we present characteristics of first two modes of NLIWs observed using high-resolution spatiotemporal data collected in a relatively flat area in the northeastern East China Sea in May 2015. Six groups of NLIWs were identified from the observations: four groups of mode-1 and two groups of mode-2. The amplitude, propagation speed, and characteristic width of mode-1 NLIWs had ranges of 4–16 m, 0.53–0.56 m s<sup>-1</sup>, and 310–610 m, respectively. The mode-2 NLIWs propagate eastward slowly with a speed less than 0.37 m s<sup>-1</sup> with a comparable amplitude of 4–14 m and longer characteristic width of 540–1920 m. Intermodal interactions may take a role in the evolution of mode-1 NLIWs west of the observational area. Our results characterizing the two modes of NLIWs highlight the significance of propagation and transformation of NLIWs and their modal interactions on a broad and shallow shelf.</p>

scholarly journals Speed and Evolution of Nonlinear Internal Waves Transiting the South China Sea

2010 ◽  
Vol 40 (6) ◽  
pp. 1338-1355 ◽  
Author(s):  
Matthew H. Alford ◽  
Ren-Chieh Lien ◽  
Harper Simmons ◽  
Jody Klymak ◽  
Steve Ramp ◽  
...  
Keyword(s):  
South China Sea ◽  
Continental Slope ◽  
Internal Waves ◽  
South China ◽  
The South China Sea ◽  
Internal Tides ◽  
Deep Basin ◽  
Nonlinear Internal Waves ◽  
The Waves ◽  
Upper Slope

Abstract In the South China Sea (SCS), 14 nonlinear internal waves are detected as they transit a synchronous array of 10 moorings spanning the waves’ generation site at Luzon Strait, through the deep basin, and onto the upper continental slope 560 km to the west. Their arrival time, speed, width, energy, amplitude, and number of trailing waves are monitored. Waves occur twice daily in a particular pattern where larger, narrower “A” waves alternate with wider, smaller “B” waves. Waves begin as broad internal tides close to Luzon Strait’s two ridges, steepening to O(3–10 km) wide in the deep basin and O(200–300 m) on the upper slope. Nearly all waves eventually develop wave trains, with larger–steeper waves developing them earlier and in greater numbers. The B waves in the deep basin begin at a mean speed of ≈5% greater than the linear mode-1 phase speed for semidiurnal internal waves (computed using climatological and in situ stratification). The A waves travel ≈5%–10% faster than B waves until they reach the continental slope, presumably because of their greater amplitude. On the upper continental slope, all waves speed up relative to linear values, but B waves now travel 8%–12% faster than A waves, in spite of being smaller. Solutions of the Taylor–Goldstein equation with observed currents demonstrate that the B waves’ faster speed is a result of modulation of the background currents by an energetic diurnal internal tide on the upper slope. Attempts to ascertain the phase of the barotropic tide at which the waves were generated yielded inconsistent results, possibly partly because of contamination at the easternmost mooring by eastward signals generated at Luzon Strait’s western ridge. These results present a coherent picture of the transbasin evolution of the waves but underscore the need to better understand their generation, the nature of their nonlinearity, and propagation through a time-variable background flow, which includes the internal tides.

scholarly journals The evolution of mode-2 nonlinear internal waves over the northern Heng-Chun Ridge south of Taiwan

2015 ◽  
Vol 22 (4) ◽  
pp. 413-431 ◽  
Author(s):  
S. R. Ramp ◽  
Y. J. Yang ◽  
D. B. Reeder ◽  
M. C. Buijsman ◽  
F. L. Bahr
Keyword(s):  
Internal Waves ◽  
High Frequency ◽  
Velocity Structure ◽  
Primary Study ◽  
Turbulent Dissipation ◽  
Nonlinear Internal Waves ◽  
Mode 2 ◽  
Sill Depth ◽  
The Waves ◽  
Very High

Abstract. Two research cruises were conducted from the R/V OCEAN RESEARCHER 3 during 05–16 August 2011 to study the generation and propagation of high-frequency nonlinear internal waves (NLIWs) over the northern Heng-Chun Ridge south of Taiwan. The primary study site was on top of a smaller ridge about 15 km wide by 400 m high atop the primary ridge, with a sill depth of approximately 600 m. A single mooring was used in conjunction with shipboard observations to sample the temperature, salinity and velocity structure over the ridge. All the sensors observed a profusion of mode-2 NLIWs. Some of the waves were solitary, while others had as many as seven evenly spaced waves per packet. The waves all exhibited classic mode-2 velocity structure with a core near 150–200 m and opposing velocities in the layers above and below. At least two and possibly three most common propagation directions emerged from the analysis, suggesting multiple generation sites near the eastern side of the ridge. The turbulent dissipation due to overturns in the wave cores was very high at order 10−4–10−3 W kg−1. The energy budget suggests that the waves cannot persist very far from the ridge and likely do not contribute to the South China Sea transbasin wave phenomenon.

scholarly journals Statistics of Nonlinear Internal Waves during the Shallow Water 2006 Experiment

2016 ◽  
Vol 33 (4) ◽  
pp. 839-846 ◽  
Author(s):  
Mohsen Badiey ◽  
Lin Wan ◽  
James F. Lynch
Keyword(s):  
Continental Shelf ◽  
Shallow Water ◽  
Internal Waves ◽  
Three Dimensional ◽  
Propagation Speed ◽  
Mapping Technique ◽  
Nonlinear Internal Waves ◽  
Ocean Environment ◽  
Reference Track ◽  
Time Varying Environment

AbstractDuring the Shallow Water Acoustic Experiment 2006 (SW06) conducted on the New Jersey continental shelf in the summer of 2006, detailed measurements of the ocean environment were made along a fixed reference track that was parallel to the continental shelf. The time-varying environment induced by nonlinear internal waves (NLIWs) was recorded by an array of moored thermistor chains and by X-band radars from the attending research vessels. Using a mapping technique, the three-dimensional (3D) temperature field for over a month of NLIW events is reconstructed and analyzed to provide a statistical summary of important NLIW parameters, such as the NLIW propagation speed, direction, and amplitude. The results in this paper can be used as a database for studying the NLIW generation, propagation, and fidelity of nonlinear internal wave models.

Energy Transport by Nonlinear Internal Waves

2007 ◽  
Vol 37 (7) ◽  
pp. 1968-1988 ◽  
Author(s):  
J. N. Moum ◽  
J. M. Klymak ◽  
J. D. Nash ◽  
A. Perlin ◽  
W. D. Smyth
Keyword(s):  
Internal Waves ◽  
Energy Flux ◽  
Energy Transport ◽  
Internal Tide ◽  
Surface Displacement ◽  
Bottom Layer ◽  
Ekman Transport ◽  
Nonlinear Internal Waves ◽  
Advection Term ◽  
The Waves

Abstract Winter stratification on Oregon’s continental shelf often produces a near-bottom layer of dense fluid that acts as an internal waveguide upon which nonlinear internal waves propagate. Shipboard profiling and bottom lander observations capture disturbances that exhibit properties of internal solitary waves, bores, and gravity currents. Wavelike pulses are highly turbulent (instantaneous bed stresses are 1 N m−2), resuspending bottom sediments into the water column and raising them 30+ m above the seafloor. The wave cross-shelf transport of fluid often counters the time-averaged Ekman transport in the bottom boundary layer. In the nonlinear internal waves that were observed, the kinetic energy is roughly equal to the available potential energy and is O(0.1) megajoules per meter of coastline. The energy transported by these waves includes a nonlinear advection term 〈uE〉 that is negligible in linear internal waves. Unlike linear internal waves, the pressure–velocity energy flux 〈up〉 includes important contributions from nonhydrostatic effects and surface displacement. It is found that, statistically, 〈uE〉 ≃ 2〈up〉. Vertical profiles through these waves of elevation indicate that up(z) is more important in transporting energy near the seafloor while uE(z) dominates farther from the bottom. With the wave speed c estimated from weakly nonlinear wave theory, it is verified experimentally that the total energy transported by the waves is 〈up〉 + 〈uE〉 ≃ c〈E〉. The high but intermittent energy flux by the waves is, in an averaged sense, O(100) watts per meter of coastline. This is similar to independent estimates of the shoreward energy flux in the semidiurnal internal tide at the shelf break.

Current and Density Observations of Packets of Nonlinear Internal Waves on the Outer New Jersey Shelf

2011 ◽  
Vol 41 (5) ◽  
pp. 994-1008 ◽  
Author(s):  
W. J. Teague ◽  
H. W. Wijesekera ◽  
W. E. Avera ◽  
Z. R. Hallock
Keyword(s):  
New Jersey ◽  
Internal Waves ◽  
Nonlinear Internal Waves

scholarly journals The evolution of Mode-2 nonlinear internal waves over the northern Heng-Chun ridge south of Taiwan

2015 ◽  
Vol 2 (1) ◽  
pp. 243-296 ◽  
Author(s):  
S. R. Ramp ◽  
Y. J. Yang ◽  
D. B. Reeder ◽  
M. C. Buijsman ◽  
F. L. Bahr
Keyword(s):  
Internal Waves ◽  
High Frequency ◽  
Velocity Structure ◽  
Primary Study ◽  
Turbulent Dissipation ◽  
Nonlinear Internal Waves ◽  
Mode 2 ◽  
Sill Depth ◽  
The Waves ◽  
Very High

Abstract. Two research cruises were conducted from the R/V OCEAN RESEARCHER 3 during 5–16 August 2011 to study the generation of high-frequency nonlinear internal waves (NLIW) over the northern Heng-Chun Ridge south of Taiwan. The primary study site, centered near 21°34' N, 120°54' E, was on top of a smaller ridge about 15 km wide by 400 m high atop the primary ridge, with a sill depth of approximately 600 m. The bottom slope was steep over both sides of the ridge, supercritical with respect to both diurnal and semidiurnal tides. The key result of the experiments is that a profusion of mode-2 NLIW were observed by all the sensors. Some of the waves were solitary while others had as many as seven evenly-spaced waves per packet. The waves all exhibited classic mode-2 velocity structure with a core near 150–200 m and opposing velocities in the layers above and below. At least two and possibly three most common propagation directions emerged from the analysis, suggesting multiple generation sites near the east side of the ridge. The turbulent dissipation due to overturns in the wave cores was very high at order 10−4–10−3 W kg−1. The energy budget suggests that the waves cannot persist very far from the ridge and likely do not contribute to the South China Sea transbasin wave phenomenon.

scholarly journals Strongly nonlinear, simple internal waves in continuously-stratified, shallow fluids

2011 ◽  
Vol 18 (1) ◽  
pp. 91-102 ◽  
Author(s):  
L. A. Ostrovsky ◽  
K. R. Helfrich
Keyword(s):  
Internal Waves ◽  
Wide Class ◽  
Vertical Structure ◽  
Initial Conditions ◽  
Layer Structure ◽  
Density Profiles ◽  
Nonlinear Internal Waves ◽  
Strongly Nonlinear ◽  
Simple Waves ◽  
Hydrostatic Approximation

Abstract. Strongly nonlinear internal waves in a layer with arbitrary stratification are considered in the hydrostatic approximation. It is shown that "simple waves" having a variable vertical structure can emerge from a wide class of initial conditions. The equations describing such waves have been obtained using the isopycnal coordinate as a variable. Emergence of simple waves from an initial Gaussian impulse is numerically investigated for different density profiles, from two- and three-layer structure to the continuous one. Besides the first mode, examples of second- and third-mode simple waves are given.

scholarly journals Shore-Based Video Observations of Nonlinear Internal Waves across the Inner Shelf *,+

2014 ◽  
Vol 31 (3) ◽  
pp. 714-728 ◽  
Author(s):  
Sutara H. Suanda ◽  
John A. Barth ◽  
Rob A. Holman ◽  
John Stanley
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Propagation Speed ◽  
Surface Expression ◽  
Inner Shelf ◽  
Average Width ◽  
Pixel Intensity ◽  
Nonlinear Internal Waves ◽  
Video Observations

Abstract Shore-based video remote sensing is used to observe and continually monitor nonlinear internal waves propagating across the inner shelf. Month-long measurements of velocity from bottom-mounted acoustic Doppler current profilers and temperature from thermistor chains at the 10- and 20-m isobaths are combined with sea surface imagery from a suite of cameras (Argus) to provide a kinematic description of 11 borelike internal waves as they propagate across the central Oregon inner shelf. The surface expression of these waves, commonly seen by eye as alternating rough and smooth bands, are identified by increased pixel intensity in Argus imagery (average width 39 ± 6 m), caused by the convergence of internal wave-driven surface currents. These features are tracked through time and space using 2-min time exposure images and then compared to wave propagation speed and direction from in situ measurements. Internal waves are refracted by bathymetry, and the measured wave speed (~0.15 m s−1) is higher than predicted by linear theory (<0.1 m s−1). Propagating internal waves are also visible in subsampled Argus pixel time series (hourly collections of 17 min worth of 2-Hz pixel intensity from a subset of locations), thus extending the observational record to times without an in situ presence. Results from this 5-month record show that the preferred sea state for successful video observations occurs for wind speeds of 2–5 m s−1. Continued video measurements and analysis of extensive existing Argus data will allow a statistical estimate of internal wave occurrence at a variety of inner-shelf locations.

Observations of nonlinear internal waves of tidal origin in the northeastern East China Sea

2021 ◽  
Author(s):  
Seung-Woo Lee ◽  
SungHyun Nam
Keyword(s):  
East China Sea ◽  
Internal Waves ◽  
Spring Tide ◽  
Propagation Speed ◽  
East China ◽  
Multiple Sources ◽  
Flat Bottom ◽  
Nonlinear Internal Waves ◽  
China Sea ◽  
Regional Circulation

<p>Oceanic nonlinear internal waves (NLIWs) play an important role in regional circulation, biogeochemistry, energetics, vertical mixing, underwater acoustics, marine engineering, and submarine navigation, most commonly generated by the interaction between barotropic tides and bathymetry. Here, we present characteristics of first mode NLIWs observed using high-resolution in-situ data collected using moored and underway temperature sensors in a relatively flat bottom in the northeastern East China Sea during May 15-28, 2015. During the experiment, totally 34 events of first mode NLIWs were identified and characterized with amplitude of 4–16 m, characteristic width of 310–610 m, propagation speed of 0.53–0.56 m s<sup>-1</sup>, and propagation direction (mainly southwestward propagation), respectively. Most NLIWs were observed during period of spring tide with phases locked to semidiurnal barotropic tides. Generation and propagation of the first mode NLIWs observed in the region are discussed in relation to satellite images and historical hydrographic data collected in the region. Our results support significance of first mode NLIWs and their interactions on turbulent mixing and regional circulation particularly in a broad and shallow continental shelves where the NLIWs generated from multiple sources propagate into multi-directions experiencing wave-wave interactions.</p>

Sign in / Sign up

Export Citation Format

Share Document