Internal tides near the Kermadec Ridge

Current meter data from the WOCE PCM-9 array, extending 1000 km eastward fr om the Kermadec Ridge northeast of New Zealand, are used to investigate the internal tide. A high degree of spatial and temporal variability in the se midiurnal tide, but not in the diurnal tide, suggests that there is a conve rsion from barotropic to baroclinic tidal energy at the semidiurnal periods . Comparison between observed tidal constituents and those predicted by the TPXO.3 model indicates that the model may be used as an estimate of the ba rotropic tide. Once the barotropic tide has been removed, the remaining sem idiurnal energy propagates predominantly at the first vertical mode phase s peed of 3.5 m s(-1), consistent with linear theory. A frequency-domain empi rical orthogonal function analysis is used to extract signals that have pha se propagation consistent with a coherent internal tide. These modes repres ent a phase-locked semidiurnal internal tide having about 0.65 of the baroc linic energy. Tidal energies at the M-2 period associated with the phase-lo cked tide are about 155 J m(-2) over the Kermadec Ridge and 98 J m(-2) over the abyssal plain east of the ridge. Total tidal power radiation along the ridge is estimated to be about 0.8 GW.