Nonlinear evolution of ocean internal solitons propagating along an inhomogeneous thermocline

Measurements of the upper ocean thermal structure show that on the continen tal shelves the thermocline depth may shoal or deepen generally depending o n the bottom topography. Thermocline shoaling and deepening cause changes i n the phase speeds of internal waves as described by linear wave theories. On the other hand, the ocean area where internal waves have variable phase speeds may be treated as a dynamically inhomogeneous medium. In this case, theories of nonlinear dispersive wave propagation in inhomogeneous media de veloped by Tappert and Zabusky [1971] may stand. We used these theories to analyze the evolution of ocean internal solitary waves passing over a seamo unt in the Gulf of Aden. The results indicate that a surprisingly sharp rec ess of an internal solitary wave packet, imaged by the space shuttle Discov ery, is a signature of spatial phase delay caused by thermocline shoaling o ver the seamount. Soliton fission due to thermocline shoaling was also obse rved in the imagery. The observed number of transmitted solitons over the s eamount agrees with theoretical predictions. Relative soliton amplitudes me asured from the imagery also agree qualitatively with predictions.