The effects of critical level absorption of oceanic internal waves by a mean flow are estimated using the Garrett and Munk (1975) model spectrum. The horizontal currents of the wave field are found to be more intense perpendicular to the mean flow than parallel to it. The cause of this anisotropy is preferential absorption of waves travelling with the mean flow. However, the current anisotropy is only half as large as would be necessary to explain Frankignoul's (1974) observations....
Ruddick, Barry. 1980. "Critical layers and the Garrett-Munk spectrum." Journal of Marine Research 38, (1). https://elischolar.library.yale.edu/journal_of_marine_research/1502