Diapycnal mixing induced by breaking internal waves over topography

Colorado State University, Fort Collins CO

Investigators

Abstract

Many noteworthy field observations indicate that diapycnal (irreversible) mixing is primarily driven by internal waves interacting with underwater topographic features. This project will model the nonlinear interactions of internal waves with topography, and will lead to new knowledge/concepts for quantifying diapycnal mixing induced by breaking internal waves. Model-data comparisons will be used to test the adequacy of mixing parameterizations. Improvements in understanding and parameterizations of diapycnal mixing from internal waves will provide a wide range of scientific broader impacts, from global climate prediction to the crucial role that internal wave driven diapycnal mixing plays in transport of nutrients for the oceanic ecosystem. Broader impacts on education stem from the training/mentoring of a graduate student through this project. Outreach efforts include the PI’s involvement in summer campus/programs coordinated by the Women and Minorities in Engineering at Colorado State University (CSU) as well as through outreach to local high school students through organized visits to the PI’s new Environmental Fluid Mechanics Laboratory at CSU. Highly resolved direct numerical simulations (DNS) and large-eddy simulations (LES) using a combination of Eulerian and Lagrangian perspectives will be employed to elucidate small-scale mixing processes/mechanisms with an eye towards parameterization of the salient physics for near boundary mixing resulting from the breaking of internal waves. The main objectives of the project are to: (1) investigate the relationships between relevant length scales and time scales for mixing of both momentum and scalar (density) using a series of high-resolution “numerical” microstructure profile studies of internal wave- topography interactions; (2) formulate parameterizations for diapycnal mixing driven by internal waves interacting with single and multiple topographic features; and (3) explain the fate of NLIWs as a result of the interaction process with topography and determine whether they contribute significantly to mixing and transport. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.