|Title||A multi-wavenumber theory for eddy diffusivities and its application to the southeast Pacific (DIMES) region|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Chen R, Gille ST, McClean JL, Flierl GR, Griesel A|
|Journal||Journal of Physical Oceanography|
AbstractA multi-wavenumber theory is formulated to represent eddy diffusivities. It expands on earlier single-wavenumber theories and includes the wide range of wavenumbers encompassed in eddy motions. In the limiting case in which ocean eddies are only composed of a single wavenumber, the multi-wavenumber theory is equivalent to the single wavenumber theory, and both show mixing suppression by the eddy propagation relative to the mean flow. The multi-wavenumber theory was tested in a region of the Southern Ocean (70°S ? 45°S, 110°W ? 20°W) that covers the Drake Passage and includes the tracer/float release locations during the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). Cross-stream eddy diffusivities and mixing lengths were estimated in this region from the single-wavenumber theory, from the multi-wavenumber theory, and from floats deployed in a global 1/10° Parallel Ocean Program (POP) simulation. Compared to the single-wavenumber theory, the horizontal structures of cross-stream mixing lengths from the multi-wavenumber theory agree better with the simulated float-based estimates at almost all depth levels. The multi-wavenumber theory better represents the vertical structure of cross-stream mixing lengths both inside and outside the Antarctica Circumpolar Current (ACC). Both the single-wavenumber and multi-wavenumber theories represent the horizontal structures of cross-stream diffusivities, which resemble the eddy kinetic energy patterns.