This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Nonlinear internal waves (NLIWs), ubiquitous features of the coastal ocean and lakes, are on the receiving end of an energy cascade initiated at large scales by the winds and tides in stratified natural water bodies. These waves transport this energy over 100km distances across gently sloping (shoaling) shelf regions and dissipate it remotely. Recent massive field-scale experiments in the South China Sea and the New Jersey Shelf have provided invaluable insight into the process of NLIW shoaling. Nonetheless, due to limitations of field measurements in space and time, a number of key questions on wave shoaling remain unanswered, namely in terms of the associated energy dissipation mechanisms, which are further complicated by the large-scale wave transformations due to variable bathymetry. To this end, small-scale numerical modeling is imperatively needed.
The project aims at the use of a fully non-hydrostatic and nonlinear parallel spectral quadrilateral sub-domain penalty method model to numerically study shoaling of NLIWs over gentle slopes. The model enables the maximum possible scale separation between wave-scale and the small-scale dissipative processes in the wave interior/footprint with optimal resolution of the latter, allowing a Reynolds number as close as possible to the oceanic value. Simulations will focus on the basic physics of wave-scale transformations due to shoaling and their impact on the three-dimensional turbulent dissipative dynamics of the NLIW-induced benthic boundary layer and subsurface trapped recirculation cores. A close comparison with field data from the above sites (including a very richly documented set of observations from the South China Sea on NLIWs and trapped cores) will establish consistency checks for the simulations, flesh out the basic physics from the measurements and provide guidance for future deployments.
Understanding the physics of turbulent dissipation in the NLIW footprint and interior is a crucial missing link in the closure of large-scale energy budgets in the ocean and lakes. Furthermore, the flow fields inside trapped cores and the NLIW-induced benthic boundary layer can drive powerful horizontal biota/nutrient transport and intense resuspension of bottom-lodged biogeochemical constituents, respectively. Beyond an enhanced description of the fundamental physics of wave shoaling, the project will offer the foundation for future investigations on how the flow fields within NLIWs directly interact with underwater ecology, acoustics and optics and impact water quality. Improved parameterizations of particulate re-suspension and near-bottom/surface dissipation may then be developed for use in larger-scale models and field data analysis.
The close comparison with South China Sea field data will initiate an active long-term collaboration between Cornell and the University of Washington. All important numerical results will be disseminated to interested members of the oceanographic community via an internet database.
Motivated by the advanced numerical methods embedded in the multi-domain solver, a tightly linked chain of educational activities seeks to initiate a reconsideration of the current paradigm in scientific computing education at the graduate/undergraduate level and to boost recruitment of high school students into science and engineering majors. Starting with graduate coursework, the proposed educational plan aims to create ocean model users who, although not developers, have a robust numerical and oceanographic expertise which is aligned with cutting edge computational methods. The restructuring of a sophomore-level course on scientific computing will allow undergraduate students to discover the potential of this research area and embrace it as a vehicle to complete their studies in the sciences and engineering, thereby establishing a consistent flux of future numerical modelers to the graduate ranks. A one-week high-school course module on internal wave simulation in lakes will introduce a diverse audience of high school students to computational modeling as an alternative to the traditional 'wet lab' and the option of future studies in applied computation in science and engineering.
