Turbulence produced by internal waves in the oceanic thermocline at mid and low latitudes

When mid-latitude internal waves are at the background state modeled by Garrett and Munk ( J. Geophys. Res. , 80: 291–297, 1975), wave-wave interactions transfer energy to dissipative scales so slowly that instabilities generate overturns not much larger than the scales at which viscosity dissipates the turbulence. Consequently, high wavenumber spectra contain only the viscous decay portion of the universal turbulent spectrum. Increases in low-wavenumber shear above background produce larger overturns and turbulence sufficiently intense to form well-developed inertial subranges. The turbulent region of the vertical spectrum is separated from the wave region by a k 3 −1 rolloff that does not vary with the amplitude of low-wavenumber shear, indicating that the wave field is saturated. At low latitudes, internal wave shear is generally more intense than at mid latitudes, but the turbulence is similar to that found with mid-latitude waves at background. Dynamically, the anomaly implies that wave-wave interactions transfer energy to dissipative scales more slowly at low latitudes than at high latitudes. Kinematically, this anomaly results from steeper slope in the rolloff range.