Data
collected during recent field deployments in the South China Sea has
been preliminarily analyzed, and reveals previously undocumented
turbulence and dissipative properties of the large-amplitude internal
waves generated in the Luzon passage. As previously documented in many
studies, these waves propagate westward toward the continental shelves
of China and Vietnam. In deep water, these waves are soliton-like
depression anomalies in the thermocline, with vertical displacement
amplitudes of order 100 m. The waves propagate with a coherent
structure across most of the basin, breaking into trains of depression
waves only after considerable shoaling, typically shoreward of the
shelf break. However, our microstructure surveys found that turbulent
kinetic energy dissipation rates were enhanced throughout the
continental slope region, extending from the 1000-m isobath to the
shelf break. Surprisingly, dissipation levels occurring in relatively
deep water on the continental slope were larger than those on the
continental shelf. This is in contrast to coastal regions, such as the
New Jersey shelf and Massachusetts Bay, where nonlinear waves are
typically most dissipative in the shallow waters of the coastal zone.
Our measurements suggest that the first-order closure of the energy
budget for Luzon generated waves occurs primarily in water deeper than
100 m.