Numerical Investigation of Nonlinear Internal Wave Generation and Breaking in Straits

The long-term goal of this research is to develop a physical understanding of the processes that lead to mixing in the ocean with the aim of using this understanding to develop parameterizations of mixing suitable for global and regional models. Of particular focus are the mixing induced by tidal flow over topography and the mixing induced by breaking nonlinear internal waves. The primary scientific objective of this study is to explore internal waves generated by tidal flow through the Luzon Strait in the region close to the sill. A particular scientific focus is nonlinear overturning and breaking within the straits leading to mixing and modification of the wave field. We examine whether transient internal hydraulic jumps are possible in the Luzon Strait, whether these jumps are released to propagate toward the topography as internal bores when the flow relaxes, and whether the bores lead to local mixing. We will explore the details of Luzon Strait topography to identify locations particularly conducive to local overturning processes. The Luzon Strait features two parallel North-South oriented ridges. We will examine how the wave fields of the two ridges interact and affect wave generation and mixing processes. We also will examine the importance of three-dimensional bathymetry in determining the locations of mixing, and the sensitivity of the nonlinear wave response to local stratification near the sill and ambient geostrophic currents. To summarize, our goals are as follows: (1) examine the dependence of nonlinear features and local breaking at the generation site on topographic shape and stratification, (2) evaluate how the interactions between the ridges affect mixing, (3) examine the extent to which the mixing processes are determined by three-dimensional topographic variations, and (4) examine the impact of seasonal variations in stratification and geostrophic currents on the length-scales and amplitude of the internal tides.