Abstract
The redistribution and dissipation of internal wave energy arising from the conversion at mid-ocean ridges of the barotropic tide is studied in a set of numerical experiments. A two-dimensional non-hydrostatic model with 100 m horizontal and 10–25 m vertical resolution is used to represent the detailed processes near an idealised ridge. Conventional internal wave beams at the tidal frequency, , appear. At the ridge crest, strong tidal energy dissipation occurs that both mixes the fluid and generates strong near-inertial oscillations radiating in near-horizontal beams. Resonant triad interaction between the tidal and inertial motions in turn produces beams at and with high shear, thus effectively mixing fluid at considerable heights above the ridge crest.
Highlights
Internal waves remain the main candidate for the mechanism by which the ocean is mixed (e.g. Thorpe, 1975)
Strong tidal energy dissipation occurs that both mixes the fluid and generates strong near-inertial oscillations radiating in near-horizontal beams
Three pairs of internal wave beams are formed at the ridge crest in the simulation forced by a barotropic tide at the M2 frequency
Summary
Internal waves remain the main candidate for the mechanism by which the ocean is mixed (e.g. Thorpe, 1975). Numerous recent studies include Khatiwala (2003); Legg and Klymak (2008) and Nikurashin and Legg (2011) The latter (hereafter NL11) provided an interesting and useful discussion of the two-dimensional problem, suggesting that the non-linear waveÁwave (resonant triad) interactions are the dominant mechanism by which mixing is controlled. The purpose of this present note is to better understand, in a somewhat simpler, even more idealised, configuration than the one used by NL11, the mechanisms by which non-linear interactions are generated in a two-dimensional stratified rotating ocean with topography. It is possible to isolate the regions of occurrence of the resonant triad interactions, and their initialisation
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