Moored Observations to Define the Structure and Energetics of Non-Linear Internal Wave Generation over the New Jersey Shelf

To further our understanding of NLIW generation, to aid our NLIW prediction ability, and to quantify NLIW effects on acoustics, optics, energy dissipation, and momentum transfer in the coastal ocean. OBJECTIVES What environmental factors define the structure and energetics of non-linear internal wave generation, and how can theses be used to predict intensity and quality of a wave packet. Specifically: • Under what conditions (stratification, barotropic forcing and topography) are NLIWs generated? What factors determine whether waves of elevation or waves of depression form? How are these influenced by the location of the shelf-break front? • What are the generation mechanisms? 1. barotropic via either a nonlinear version of Baines ’ (1982), or a controlled hydraulic flow which is released at low Froude numbers; or, 2. baroclinic, whereby a nearly-linear internal tide is generated and undergoes nonlinear transformations either locally or after having propagated many wavelengths. • What are the conversion efficiencies (i.e., the rates of energy transfer from linear to nonlinear waves, or from barotropic to baroclinic waves), and what fraction is dissipated locally? What fraction radiates away from the shelf break (forming the red beams in figure 2). • How do the near-bottom and near-surface signatures differ for these two types of waves. How important is the bottom stress? Can a surface expression for waves of elevation be detected? APPROACH Moored observations are used to capture the full water column variability of density (sound speed) and velocity. From these we compute barotropic and baroclinic energy density and energy flux. Divergences of energy flux are used to assess generation location and conversion efficiencies, and phasing of baroclinic signals (and their relationship to the barotropic tide) will elucidate mechanisms