[1] The conversion of depression nonlinear internal solitons to elevation internal waves has been observed twice at the South China Sea continental shelf break. Shipboard X-band radar, tow-yo CTD, ADCP and high frequency acoustic flow visualization of the process are presented. The data focuses on up slope propagation of depression internal solitons from a water depth of $264 m to a water depth of $110 m. Dissipation by large amplitude shear instabilities was observed. The kinetic energy density was found to be a decreasing monotonic function of range with an energy dissipation rate coefficient of 0.063 km À1 . The rate of energy dissipation over the $16.5 km soliton propagation path was 0.17 W/m/m. Simple numerical models of the waveform evolution are qualitatively compared to the observations. The observations, extracted scale parameters and dissipation rates should be useful for testing a variety of evolution equation representations of internal soliton propagation.INDEX TERMS: 4544 Oceanography: Physical: Internal and inertial waves; 4568 Oceanography: Physical: Turbulence, diffusion, and mixing processes; KEYWORDS: Internal waves, solitons, fine structure mixing, dissipation Citation: Orr, M. H., and P. C. Mignerey, Nonlinear internal waves in the South China Sea: Observation of the conversion of depression internal waves to elevation internal waves,

We report observations of isolated lenses of constant-temperature water embedded in the permanent thermocline in the Sargasso Sea. These features are observed to have vertical extents of •<220 m, horizontal dimensions of •<65 km, and residence depths near 700 m. A dynamic model is constructed which permits a balance among the pressure gradient, Coriolis, and cyclostrophic forces and maintains the lens against gravitational collapse. A result is that anticyclonic rim velocities approaching 20 cm s -• are permitted and that these eddies have finite radii of the order of 50 km, at which their thicknesses fall to zero.

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The temporal signature and source location of an acoustic pulse propagating in an oceanic waveguide is estimated from passively sensed multichannel data on a vertical hydrophone array. A theoretical solution for this inverse source problem is presented that incorporates both a broadband generalization of matched-field processing to estimate the source location, and a Bayesian based deconvolution algorithm operating on multichannel array data to extract the source signature. The algorithms are implemented on a massively parallel computer architecture. The theory was tested on experimental data using a chirp signal recorded on a vertical hydrophone array located approximately one convergence zone from the source. Results indicate that deconvolving the Green’s function using multichannel data is important for stabilizing the inversion in the presence of environmental mismatch. The additional information about the source time series, obtained over slightly different propagation channels, limits the solution space of the usual (ill-posed) single-sensor deconvolution problem and leads to very good reconstructions of the source signature.

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