scholarly journals Eikonal Calculations for Energy Transfer in the Deep-Ocean Internal Wave Field near Mixing Hotspots

2017 ◽  
Vol 47 (1) ◽  
pp. 199-210 ◽  
Author(s):  
Takashi Ijichi ◽  
Toshiyuki Hibiya
Keyword(s):  
Energy Transfer ◽  
Internal Wave ◽  
Wave Field ◽  
Vertical Velocity ◽  
Deep Ocean ◽  
Wave Spectra ◽  
Scale Separation ◽  
Transfer Rates ◽  
Calculated Energy ◽  
Internal Wave Field

AbstractIn the proximity of mixing hotspots in the deep ocean, the observed internal wave spectra are usually distorted from the Garrett–Munk (GM) spectrum and are characterized by the high energy level E as well as a shear–strain ratio Rω quite different from that of the GM spectrum. On the basis of the eikonal theoretical model, Ijichi and Hibiya (IH) recently proposed the revised finescale parameterization of turbulent dissipation rates in the distorted internal wave field, although the vertical velocity associated with background internal waves and the strict WKB scale separation, for example, were not taken into account. To see the effects of such simplifying assumptions on the revised parameterization, this study carries out a series of eikonal calculations for energy transfer through various internal wave spectra distorted from the GM. Although the background vertical velocity and the strict WKB scale separation somewhat affect the calculated energy transfer rates, their parameter dependence is confirmed as expected; the calculated energy transfer rates ε follow the basic scaling ε ∝ E2N2f with the local buoyancy frequency N and the local inertial frequency f and exhibit strong Rω dependence quite similar to that predicted by IH.

scholarly journals Can barotropic tide–eddy interactions excite internal waves?

2013 ◽  
Vol 721 ◽  
pp. 1-27 ◽  
Author(s):  
M.-P. Lelong ◽  
E. Kunze
Keyword(s):  
Internal Wave ◽  
Wave Field ◽  
Internal Waves ◽  
Tidal Current ◽  
Deep Ocean ◽  
Wave Excitation ◽  
Barotropic Tide ◽  
Internal Wave Field ◽  
Flow Components ◽  
Internal Wave Generation

AbstractThe interaction of barotropic tidal currents and baroclinic geostrophic eddies is considered theoretically and numerically to determine whether energy can be transferred to an internal wave field by this process. The eddy field evolves independently of the tide, suggesting that it acts catalytically in facilitating energy transfer from the barotropic tide to the internal wave field, without exchanging energy with the other flow components. The interaction is identically zero and no waves are generated when the barotropic tidal current is horizontally uniform. Optimal internal wave generation occurs when the scales of tide and eddy fields satisfy resonant conditions. The most efficient generation is found if the tidal current horizontal scale is comparable to that of the eddies, with a weak maximum when the scales differ by a factor of two. Thus, this process is not an effective mechanism for internal wave excitation in the deep ocean, where tidal current scales are much larger than those of eddies, but it may provide an additional source of internal waves in coastal areas where horizontal modulation of the tide by topography can be significant.

Nonlinear energy transfer and the energy balance of the internal wave field in the deep ocean

1976 ◽  
Vol 74 (2) ◽  
pp. 375-399 ◽  
Author(s):  
Dirk J. Olbers
Keyword(s):  
Energy Transfer ◽  
Energy Balance ◽  
Internal Wave ◽  
Wave Field ◽  
Wave Spectrum ◽  
Fluid Motion ◽  
Deep Ocean ◽  
Nonlinear Interactions ◽  
Nonlinear Energy Transfer ◽  
Spectral Models

The source function describing the energy transfer between the components of the internal wave spectrum due to nonlinear interactions is derived from the Lagrangian of the fluid motion and evaluated numerically for the spectral models of Garrett & Munk (1972a, 1975). The characteristic time scales of the transfer are found to be typically of the order of some days, so that nonlinear interactions will play an important role in the energy balance of the wave field. Thus implications of the nonlinear transfer within the spectrum for generation and dissipation processes are considered.

scholarly journals Observed Eddy–Internal Wave Interactions in the Southern Ocean

2020 ◽  
Vol 50 (10) ◽  
pp. 3043-3062
Author(s):  
Jesse M. Cusack ◽  
J. Alexander Brearley ◽  
Alberto C. Naveira Garabato ◽  
David A. Smeed ◽  
Kurt L. Polzin ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Southern Ocean ◽  
Internal Wave ◽  
Wave Field ◽  
Internal Waves ◽  
Temporal Variability ◽  
Mesoscale Eddy ◽  
Linear Wave ◽  
Wave Interactions ◽  
Internal Wave Field

AbstractThe physical mechanisms that remove energy from the Southern Ocean’s vigorous mesoscale eddy field are not well understood. One proposed mechanism is direct energy transfer to the internal wave field in the ocean interior, via eddy-induced straining and shearing of preexisting internal waves. The magnitude, vertical structure, and temporal variability of the rate of energy transfer between eddies and internal waves is quantified from a 14-month deployment of a mooring cluster in the Scotia Sea. Velocity and buoyancy observations are decomposed into wave and eddy components, and the energy transfer is estimated using the Reynolds-averaged energy equation. We find that eddies gain energy from the internal wave field at a rate of −2.2 ± 0.6 mW m−2, integrated from the bottom to 566 m below the surface. This result can be decomposed into a positive (eddy to wave) component, equal to 0.2 ± 0.1 mW m−2, driven by horizontal straining of internal waves, and a negative (wave to eddy) component, equal to −2.5 ± 0.6 mW m−2, driven by vertical shearing of the wave spectrum. Temporal variability of the transfer rate is much greater than the mean value. Close to topography, large energy transfers are associated with low-frequency buoyancy fluxes, the underpinning physics of which do not conform to linear wave dynamics and are thereby in need of further research. Our work suggests that eddy–internal wave interactions may play a significant role in the energy balance of the Southern Ocean mesoscale eddy and internal wave fields.

scholarly journals Estimates of wind power and radiative near-inertial internal wave flux

2020 ◽  
Vol 70 (11) ◽  
pp. 1357-1376
Author(s):  
Georg S. Voelker ◽  
Dirk Olbers ◽  
Maren Walter ◽  
Christian Mertens ◽  
Paul G. Myers
Keyword(s):  
Energy Transfer ◽  
Internal Wave ◽  
Wind Power ◽  
Mixed Layer ◽  
North Atlantic ◽  
Mixed Layer Depth ◽  
Deep Ocean ◽  
Wave Radiation ◽  
Buoyancy Frequency ◽  
The North

Abstract Energy transfer mechanisms between the atmosphere and the deep ocean have been studied for many years. Their importance to the ocean’s energy balance and possible implications on mixing are widely accepted. The slab model by Pollard (Deep-Sea Res Oceanogr Abstr 17(4):795–812, 1970) is a well-established simulation of near-inertial motion and energy inferred through wind-ocean interaction. Such a model is set up with hourly wind forcing from the NCEP-CFSR reanalysis that allows computations up to high latitudes without loss of resonance. Augmenting the one-dimensional model with the horizontal divergence of the near-inertial current field leads to direct estimates of energy transfer spectra of internal wave radiation from the mixed layer base into the ocean interior. Calculations using this hybrid model are carried out for the North Atlantic during the years 1989 and 1996, which are associated with positive and negative North Atlantic Oscillation index, respectively. Results indicate a range of meridional regimes with distinct energy transfer ratios. These are interpreted in terms of the mixed layer depth, the buoyancy frequency at the mixed layer base, and the wind field structure. The average ratio of radiated energy fluxes from the mixed layer to near-inertial wind power for both years is approximately 12%. The dependence on the wind structure is supported by simulations of idealized wind stress fronts with variable width and translation speeds.

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