Equatorial Macro Turbulence: Extending Mid-Latitude Macro Turbulence Studies to the Equatorial Region

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In the mid-latitudes, the large-scale turbulent ocean circulation commonly evolves towards a pattern of large-scale jets and vortices, which is known as geostrophic turbulence. While the theory of geostrophic turbulence has been studied for decades, it has only been observed relatively recently and those observations suggest that it is ubiquitous throughout the extratopical ocean. Similar observations made in the equatorial ocean, prompted this scientist to consider how the theory of geostrophic turbulence must be modified in the equatorial ocean where the relative change in the Coriolis parameter is large and geostrophy fails. In this study, he will employ theory and a hierarchy of numerical models to develop a picture of macro turbulence in the equatorial region which will complement existing theories of geostrophic turbulence. One aspect of the theory that is being considered is known as the Rhines effect: alternating zonal jets form due to the interaction of Rossby waves and the turbulence. The length scale at which this happens varies near the equator more rapidly than in mid-latitudes and hence the dynamics are more complex. The cascade of energy is also being considered. In simple one-layer geostrophic turbulence, the concurrent conservation of energy and enstrophy causes motions to evolve towards larger scales. When the relatively rapid change in the Coriolis parameter is considered, then energy must not only cascade towards higher length scales but also towards larger deformation radii and hence towards the equator. In addition to the intellectual merit of this work, this project will support an innovative pilot program where a U.S. graduate student in physical oceanography will spend three months in Kenya to facilitate scientific collaborations between the industrialized and developing world. This pilot program will be done in coordination with the Intergovernmental Oceanographic Commission.