Mode‐2 internal waves impact on acoustic signal properties.

2010 ◽  
Vol 127 (3) ◽  
pp. 1973-1973 ◽  
Author(s):  
Marshall Orr
Keyword(s):  
Internal Waves ◽  
Acoustic Signal ◽  
Mode 2

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>

The temporal variability of near-inertial internal waves in an internal tide beam

2021 ◽  
Author(s):  
Jonas Löb ◽  
Monika Rhein
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Temporal Variability ◽  
Internal Tide ◽  
Internal Tides ◽  
Inertial Waves ◽  
Energy Fluxes ◽  
Wind Event ◽  
Mode 2 ◽  
Inertial Energy

<p>Low mode internal waves in the stratified ocean are generated by the interaction between barotropic tides and seafloor topography and by the wind field in the near-inertial range. They are crucial for interior mixing and for the oceanic energy pathways, since they carry a large portion of the energy of the entire internal wave field. Long-term observations of energy fluxes of internal waves are sparse. The aim of this work is to study the temporal variability of wind generated low mode near-inertial internal waves inside an internal tide beam emanating from seamounts south of the Azores. For this, 20 months of consecutive mooring observations are used to calculate the mode 1 and mode 2 near-inertial energy fluxes as well as kinetic and potential energies. The gathered time series of near-inertial internal wave energy flux is not steady due to its intermittent forcing and is neither dominated by either mode 1 or mode 2. It shows a peak induced by a distinct strong wind event which is directly linked to wind-power input into the mixed layer north-east of the mooring location, and allows a comparison between the wind event and a background state. Furthermore, indications of non-linear interactions of the near-inertial waves with the internal tides in the form of resonant triad interaction and non-linear self-interaction have been found. This study provides new insights on the relative importance of single wind events and reinforces the assumption of a global non-uniform distribution of near-inertial energy with emphasis in regions where these events occur often and regularly. It furthermore displays its importance to be adequately incorporated into ocean general circulation models and in generating ocean mixing estimates by near-inertial waves as a similarly important component next to the internal tides.</p>

scholarly journals Generation of mode-2 internal waves in a two-dimensional stratification by a mode-1 internal wave

Wave Motion ◽  
2018 ◽  
Vol 83 ◽  
pp. 227-240
Author(s):  
Jianjun Liang ◽  
Tao Du ◽  
Xiaoming Li ◽  
Mingxia He
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Two Dimensional ◽  
Mode 2

Observations of Large-Amplitude Mode-2 Nonlinear Internal Waves on the Australian North West Shelf

2019 ◽  
Vol 49 (1) ◽  
pp. 309-328 ◽  
Author(s):  
Matthew D. Rayson ◽  
Nicole L. Jones ◽  
Gregory N. Ivey
Keyword(s):  
Internal Waves ◽  
Large Amplitude ◽  
Transition Period ◽  
Local Mode ◽  
Driving Mechanism ◽  
Length Scale ◽  
North West ◽  
Nonlinear Internal Waves ◽  
Mode 2 ◽  
Amplitude Mode

AbstractLarge-amplitude mode-2 nonlinear internal waves were observed in 250-m-deep water on the Australian North West shelf. Wave amplitudes were derived from temperature measurements using three through-the-water-column moorings spaced 600 m apart in a triangular configuration. The moorings were deployed for 2 months during the transition period between the tropical monsoon and the dry season. The site had a 25–30-m-amplitude mode-1 internal tide that essentially followed the spring–neap tidal cycle. Regular mode-2 nonlinear wave trains with amplitudes exceeding 25 m, with the largest event exceeding 50 m, were also observed at the site. Overturning was observed during several mode-2 events, and the relatively high wave Froude number and steepness (0.15) suggested kinematic (convective) instability was likely to be the driving mechanism. The presence of the mode-2 waves was not correlated with the tidal forcing but rather occurred when the nonlinear steepening length scale was smaller than the distance from the generation region to the observation site. This steepening length scale is inversely proportional to the nonlinear parameter in the Korteweg–de Vries equation, and it varied by at least one order of magnitude under the evolving background thermal stratification over the observation period. Despite the complexity of the internal waves in the region, the nonlinear steepening length was shown to be a reliable indicator for the formation of large-amplitude mode-2 waves and the rarer occurrence of mode-1 large-amplitude waves. A local mode-2 generation mechanism caused by a beam interacting with a pycnocline is demonstrated using a fully nonlinear numerical solution.

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 Generation of mode 2 internal waves by the interaction of mode 1 waves with topography

2019 ◽  
Vol 880 ◽  
pp. 799-830 ◽  
Author(s):  
Zihua Liu ◽  
Roger Grimshaw ◽  
Edward Johnson
Keyword(s):  
Internal Waves ◽  
Mode Coupling ◽  
Wave Amplitude ◽  
Fluid Model ◽  
Wave Theory ◽  
Topographic Slope ◽  
Long Wave ◽  
Mode 2 ◽  
Generation Mechanisms ◽  
Infinite Set

Oceanic internal waves can be decomposed into an infinite set of modes, and the dominant internal mode 1 waves have been extensively investigated. Although mode 2 waves have been observed, they have not received comparable attention, especially the generation mechanisms. In this work, we examine the generation of mode 2 internal waves by the interaction of mode 1 waves with topography. We use a coupled linear long-wave theory with mode coupling through topography, combined with evolution using a Korteweg–de Vries model, to predict the mode 2 wave amplitude, in an ideal three-layer fluid model, in a smooth density stratification and in two realistic oceanic settings. We find that the mode 2 wave amplitude is usually much smaller than the incident mode 1 wave amplitude and is quite sensitive to the pycnocline thickness, topographic slope and background stratification.

scholarly journals Internal waves of mode 2 in the Black Sea

2019 ◽  
Vol 488 (5) ◽  
pp. 555-559
Author(s):  
A. N. Serebryany ◽  
E. E. Khimchenko
Keyword(s):  
Water Column ◽  
Internal Waves ◽  
Black Sea ◽  
Horizontal Component ◽  
The Black Sea ◽  
Short Period ◽  
Mode 2 ◽  
Vertical Displacements

The results of the first observations of mode 2 internal waves in the Black Sea are presented. The measurements were carried out on the Crimean shelf from the MGI platform in July 2011. In the period after the sweep, when measurements were taken, firstly mode 1 inertial internal waves were observed, and then mode 2 one. The oscillations of mode 2 were most pronounced in the vertical displacements of the water column, reaching amplitudes of 10 m. The features of mode 2 were also noted in fluctuations of the horizontal component of the currents. Along with the registration of mode 2 inertial internal waves, the appearance of short-period internal waves of mode 2 was also noted.

scholarly journals Generation of Internal Lee Waves by Lateral Circulation in a Coastal Plain Estuary

2019 ◽  
Vol 49 (7) ◽  
pp. 1687-1697
Author(s):  
Xiaohui Xie ◽  
Ming Li
Keyword(s):  
Internal Waves ◽  
Lateral Flow ◽  
Coastal Plain Estuary ◽  
Deep Channel ◽  
Mode 2 ◽  
Lee Waves ◽  
Lee Wave ◽  
Lateral Circulation ◽  
Internal Hydraulic Jump ◽  
Internal Bores

AbstractRecent mooring observations at a cross-channel section in Chesapeake Bay showed that internal solitary waves regularly appeared during certain phases of a tidal cycle and propagated from the deep channel to the shallow shoal. It was hypothesized that these waves resulted from the nonlinear steepening of internal lee waves generated by lateral currents over channel-shoal topography. In this study numerical modeling is conducted to investigate the interaction between lateral circulation and cross-channel topography and discern the generation mechanism of the internal lee waves. During ebb tides, lateral bottom Ekman forcing drives a counterclockwise (looking into estuary) lateral circulation, with strong currents advecting stratified water over the western flank of the deep channel and producing large isopycnal displacements. When the lateral flow becomes supercritical with respect to mode-2 internal waves, a mode-2 internal lee wave is generated on the flank of the deep channel and subsequently propagates onto the western shoal. When the bottom lateral flow becomes near-critical or supercritical with respect to mode-1 internal waves, the lee wave evolves into an internal hydraulic jump. On the shallow shoal, the lee waves or jumps evolve into internal bores of elevation.

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