Vertical energy propagation of inertial waves: A vector spectral analysis of velocity profiles

Vertical propagation of near-inertial period waves has been detected in a series of recent velocity profiles by a technique of vector spectral analysis. This method, previously applied to vector series in time, has been used to study the vertical spatial structure of velocity profiles obtained in the Mid-Ocean Dynamics Experiment (MODE). Prior to the use of spectral analysis, however, it is necessary to minimize the influence of vertical variations of the Brunt-Viiisiilii frequency. The procedure was to normalize the current amplitudes and stretch the vertical coordinate according to a WKB scheme. The vector spectral analysis, applied to the normalized and stretched profiles, yielded wave polarization estimates which are related to the sign of the vertical group velocity of internal waves. The analysis of a set of velocity profiles indicates that the net energy flux of the waves near the inertial frequency is downward. One of the striking aspects of deep ocean velocity profiles is the presence of energetic depth- and time-dependent current fluctuations. Although they are commonly stronger in the thermocline, these velocity fluctuations are observed throughout the water column. Zones of current on one profile usually will reappear on a later profile with a somewhat