A Department of Atmospheric and Oceanic Sciences seminar presented by Kaushik Srinivasan, Scripps Institution of Oceanography, University of California, San Diego
Variability of eddy-driven jets in the ACC manifests in the form of enhanced eddy activity, steering and jet drift. In particular, drift or migration of jets has been identified in satellite altimetry, primitive equation models and in quasi-geostrophic models. Using the barotropic quasi-geostrophic model, we show that jet drift is a consequence of breaking reflection symmetry either by topography, or by the spatial structure of small-scale forcing. In earlier idealized studies, jet drift has been described as an exceptional phenomenon requiring, for instance, topography in an essential way. But, generically, reflection symmetry is broken and jet-drift is the rule rather than the exception. For example, we show that drift occurs even with a flat bottom: in the absence of topography, jets can persistently drift in the meridional direction if the forcing breaks reflection symmetry. This symmetry argument can also be generalized to the two-layer model, in which topography induces drift of the jets driven by baroclinic instability.