Short-period internal waves in the sea

Groups of surface gravity waves induce horizontally varying Stokes drift that drives convergence of water ahead of the group and divergence behind. The mass flux divergence associated with spatially variable Stokes drift pumps water downwards in front of the group and upwards in the rear. This ‘Stokes pumping’ creates a deep Eulerian return flow that sets the isopycnals below the wave group in motion and generates a trailing wake of internal gravity waves. We compute the energy flux from surface to internal waves by finding solutions of the wave-averaged Boussinesq equations in two and three dimensions forced by Stokes pumping at the surface. The two-dimensional (2-D) case is distinct from the 3-D case in that the stratification must be very strong, or the surface waves very slow for any internal wave (IW) radiation at all. On the other hand, in three dimensions, IW radiation always occurs, but with a larger energy flux as the stratification and surface wave (SW) amplitude increase or as the SW period is shorter. Specifically, the energy flux from SWs to IWs varies as the fourth power of the SW amplitude and of the buoyancy frequency, and is inversely proportional to the fifth power of the SW period. Using parameters typical of short period swell (e.g. 8 s SW period with 1 m amplitude) we find that the energy flux is small compared to both the total energy in a typical SW group and compared to the total IW energy. Therefore this coupling between SWs and IWs is not a significant sink of energy for the SWs nor a source for IWs. In an extreme case (e.g. 4 m amplitude 20 s period SWs) this coupling is a significant source of energy for IWs with frequency close to the buoyancy frequency.

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Intense short-period internal waves in the ocean

Journal of Marine Research ◽

10.1357/0022240053693879 ◽

2005 ◽

Vol 63 (1) ◽

pp. 227-261 ◽

Cited By ~ 21

Author(s):

Konstantin Sabinin ◽

Andrey Serebryany

Keyword(s):

Internal Waves ◽

Short Period

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Monitoring short-period internal waves in the White Sea

Izvestiya Atmospheric and Oceanic Physics ◽

10.1134/s0001433816090309 ◽

2016 ◽

Vol 52 (9) ◽

pp. 951-960 ◽

Cited By ~ 2

Author(s):

A. V. Zimin ◽

I. E. Kozlov ◽

O. A. Atadzhanova ◽

B. Chapron

Keyword(s):

Internal Waves ◽

White Sea ◽

The White Sea ◽

Short Period

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Short-Period Internal Waves under an Ice Cover in Van Mijen Fjord, Svalbard

Advances in Meteorology ◽

10.1155/2011/573269 ◽

2011 ◽

Vol 2011 ◽

pp. 1-6

Author(s):

E. G. Morozov ◽

S. V. Muzylev ◽

A. S. Shestov ◽

A. V. Marchenko

Keyword(s):

Internal Waves ◽

Ice Cover ◽

Velocity Fluctuations ◽

Short Period

Temperature and velocity fluctuations measured in Van Mijen Fjord in Svalbard and interpreted as the fluctuations induced by internal waves revealed the existence of short-period internal waves with an amplitude of approximately 1 m and a period of approximately 5–10 min that correlate with the ice cover fluctuations of the same period with an amplitude of a few millimeters.

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Probabilistic Characteristics of Intensive Short-Period Internal Waves in the Sea of Japan

Physical Oceanography ◽

10.22449/1573-160x-2020-5-501-513 ◽

2020 ◽

Vol 27 (5) ◽

Author(s):

M. V. Kokoulina ◽

O. E. Kurkina ◽

E. A. Rouvinskaya ◽

A. A. Kurkin ◽

◽

...

Keyword(s):

Internal Waves ◽

Sea Of Japan ◽

Peter The Great Bay ◽

Statistical Characteristics ◽

The Sea Of Japan ◽

Peter The Great ◽

Short Period ◽

Wave Heights ◽

Log Normal ◽

Log Normal Distribution

Purpose. The paper is aimed at studying the regional features of the internal waves’ field in the Sea of Japan (the Peter the Great Bay) based on the field data, namely, determination of the internal waves’ statistical characteristics that can be used to predict possibility of generating the waves of extreme amplitudes. Methods and Results. The records of water temperature variability in the Peter the Great Bay (the depth at the point of measurements is 42 m) obtained for October 11 – 20, 2011 were used as the initial data. Sampling frequency of the records was 1 s that permitted to analyze the shape of the short-period internal waves. The data on the salinity vertical distribution near the measurement point was also used. The law of the power density spectrum decay (as applied to the studied record) is well described by the Garrett – Munk model for the Sea of Japan zone being under consideration. The calculated temporal series of density were applied for obtaining the basic statistical characteristics including the statistical moments. Besides, empirical distribution for such parameters as the wave heights, periods and steepness and the wave slope amplitude was approximated by the log-normal distribution law and analyzed. The expected wave heights were forecasted using the Poisson statistics. Conclusions. It is shown that the probabilistic characteristics of the internal waves are described well by the log-normal distribution. Based on repeatability of the internal waves’ heights, probability of appearance of intensive disturbances is estimated. It is shown that within 10 days, occurrence of a short-period wave with the height not less than 7 m is guaranteed at the observation point at the 42 m depth. Keywords intensive internal waves, in situ data, probabilistic characteristics of extreme waves, shelf, Sea of Japan.

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Characteristics of Short-Period Internal Waves in the Avacha Bay Based on the In Situ and Satellite Observations in August-September, 2018

Physical Oceanography ◽

10.22449/1573-160x-2020-3-278-289 ◽

2020 ◽

Vol 27 (3) ◽

Author(s):

E. I. Svergun ◽

◽

A. V. Zimin ◽

◽

...

Keyword(s):

Internal Waves ◽

Satellite Images ◽

Remote Sensing Data ◽

Water Area ◽

Satellite Observations ◽

Maximum Height ◽

Shallow Water Area ◽

Short Period ◽

Avacha Bay

Purpose. The paper is aimed at evaluating the characteristics of short-period internal waves in different regions of the Avacha Bay in the Рacific Ocean concerning their hydrological and morphometric conditions. Methods and Results. The characteristics of internal waves are assessed through synthesizing the results of the in situ studies in the Avacha Bay in August-September, 2018, the high-resolution remote sensing data and the results of tidal modeling. The data of the in situ and satellite observations of internal waves were also directly compared. The results show that in the shallow part of the Avacha Bay, the waves, whose heights are from 10 to 15 m were observed. They constitute 10 % of the total number of cases. In the deep-water part of the bay, the internal waves are also often observed, but their maximum height does not exceed 10 m. The satellite images show 72 manifestations of short-period internal waves. Some of them spread to the coast with a tidal frequency from the generation source located around the 500 m isobath where the bottom abruptly slows down. Conclusions. The results of the investigation revealed a pronounced relationship between the wave trains recorded in the shallow-water area and the semidiurnal tidal dynamics. Analysis of the hydrological situation and the satellite images permitted to assume that the internal waves could be generated as a result of not only a barotropic tide collapse, but also due to the inertial oscillations of the frontal zone formed by the Kamchatka current meanders in the presence of a shallow sharpened pycnocline. Having been analyzed, the synchronous satellite and in situ observations made it possible to find out that the internal waves of the 5–8 m height were distinctly manifested on the sea surface in case the pycnocline depth was 10–20 m.

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