A three-dimensional nonhydrostatic numerical model is used to calculat
e nonlinear energy transfers within decaying Garrett-Munk internal wav
efields. Inviscid wave interactions are calculated over horizontal sca
les from about 1 to 80 km and for vertical mode numbers less than abou
t 40 in an exponentially stratified model ocean 2000 m deep. The rate
of energy transfer from these scales to smaller, numerically damped sc
ales is used to make predictions of the dissipation rate epsilon in th
e open ocean midlatitude thermocline. In agreement with the theoretica
l analyses based on resonant interaction and eikonal theories, the sim
ulation results predict epsilon proportional to <(E)over tilde (2)> N-
2, where (E) over tilde and N are the internal wave energy density and
the ambient buoyancy frequency respectively. The magnitudes of the si
mulated dissipation rates are shown to be in good agreement with the d
issipation measurements taken from six diverse sites in the midlatitud
e thermocline. The results suggest that the rates of dissipation and m
ixing in the ocean thermocline are controlled by the nonlinear dynamic
s of the large-scale energy-containing internal waves.