Waves, Langmuir Cells and the Upper Ocean Boundary Layer Departmental Research Initiative

This initiative is fully subscribed.

The dynamics within the upper ocean boundary layer (OBL) are critical to the coupling between the atmosphere, the wave surface and the deeper ocean. Most of the energy and momentum transferred from the wind to the water column passes through the surface wave field, with some of that energy captured locally by wave breaking and wave-current interactions while the residual energy propagates away as swell. The surface wind forcing helps to set the mixed layer depth over much of the ocean, but the details of the mechanisms through which this occurs remain elusive.

An improved understanding of the complexities of the coupling between the surface wave field and the OBL is not only central to improved modeling of the physical environment, but also to predicting other fluxes through the ocean surface such as the transmission of electromagnetic energy. The dynamic details of the OBL impact the vertical profiles of essentially all physical, chemical, biological, optical and acoustic variables in the upper ocean, and it must be better understood to allow for more effective observation and modeling of the marine environment.

To address this issue, the Office of Naval Research (ONR) is supporting a five-year department research initiative (DRI) to better understand the interplay between waves, Langmuir cells and the upper OBL.

Goal

The initiative's goal is to explore the upper ocean physics necessary to advance our understanding of the fluxes into and across the ocean mixed layer, including surface waves and wave breaking, Langmuir cells and wave-current interaction. Activities to be funded under this initiative may include:

  • The generation of a comprehensive set of observations under a variety of environmental conditions that will provide the information necessary to test existing hypotheses concerning the dynamics of the OBL, develop new theories for understanding fluxes across the ocean surface, and a provide a stringent metric for verification and validation of emerging DNS/LES models for the next decade.
  • High-resolution modeling of the upper ocean mixed layer, wave surface and atmospheric boundary layer. There is the potential for a fully coupled physical model, incorporating all of the relevant ocean, wave and atmospheric dynamics, to be designated as a DoD challenge project and provided significant computational resources through the DoD’s High-Performance Computing facilities.
  • Development of new theoretical ideas concerning the interactions between currents, the OBL and the surface wave field, including wave breaking and the injection of turbulence, interactions between breaking waves and Langmuir cells, extensions or reformulations of Craik-Leibovich theory on fine scales in the presence of breaking waves, and interactions between OBL dynamics, waves and horizontal ocean fronts in regions where both turbulence and submesoscale dynamics are important.

The DRI is expected to run for five years (FY13-FY17). In years one and two, the chosen investigators will focus on planning the field program, including theoretical development, modeling and simulation, and testing and design of observational systems. The primary field effort will occur in the third year (FY15), followed by two years of data analysis and synthesis of results. The overall effort will require integration of theory, observation and modeling to accelerate the discovery and understanding of the upper OBL.

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