Energy decay along an internal tide beam in a global ocean model

Abstract:

Internal-tide energy decay in realistically forced global ocean models has been mostly studied in the diurnal and semi-diurnal tidal bands. It is unclear how much of this energy is scattered out of these tidal bands, e.g., to higher harmonics, due to nonlinear processes. Internal tides from some generation sites, such as the Amazon shelf and the Nicobar and Andaman island chain, have very large amplitudes. These internal tides break into solitary waves due to non-hydrostatic dispersion. In HYCOM, a hydrostatic model, this process is partially simulated by numerical dispersion. However, it is yet unknown how the dissipation of internal tides is affected by the numerical dispersion in hydrostatic models. In this study we use the method of vertical modes to analyze the wave-wave interaction and dissipation processes in realistically forced global HYCOM simulations with 4-km horizontal resolution and 41 layers. Results are shown for waves radiating from the Amazon shelf and the Nicobar and Andaman island chain.