Nonlinear Processes in Oceanic and Atmospheric Flows

Presentation

Baroclinic Eddy Fluxes in Quasi-Geostrophic Turbulence with Simple Topography

Author: Andrew F. Thompson, University of Cambridge.

Names and affiliation of other authors:

Oral or poster: Oral presentation

Downloadable talk file:

Topography and transport in baroclinic turbulence

(NLOA_AFThompson.pdf, 6738426 bytes)

Abstract:
Jets are a well-known feature of the Southern Ocean's Antarctic Circumpolar Current. Recent evidence from satellite altimetry and numerical models suggests that zonal jets are also a robust feature of the mid-latitude ocean basins. The characteristics of these jets differ, however, with satellite altimetry indicating that Southern Ocean jets have a narrower, ribbon-like appearance and a greater tendency to meander. Topographical features, continental boundaries, and differences in the strength and vertical structure of mean flows may all contribute to the dissimilarity of mid-latitude and Southern Ocean jets.
This study considers the influence of simple topography on both the formation and transport properties of coherent structures (jets and eddies) in forced-dissipative, quasi-geostrophic turbulence. The experimental framework is a series of two-layer, baroclinically-unstable simulations in a doubly-periodic domain forced by an imposed vertical shear. These large-domain simulations allow the turbulence to achieve statistically-steady equilibrium states with multiple jets. The sensitivity of the jet structure to topographical slopes, sinusoidal ridges and bumps is explored. Besides providing a mechanism for steering through potential vorticity conservation, topography can also alter the equilibrated energy levels and eddy heat transport. Effective diffusivity calculations are presented to provide insight into how jets and eddies enable or inhibit mixing.

*Satellite images from NASA and ESA

Nonlinear Processes in Oceanic and Atmospheric Flows. July 2-4, 2008. Castro Urdiales, Cantabria, Spain.