Formation and maintenance of zonally elongated transients in the ocean

Anisotropic, zonally elongated flow structures represent a unique feature of atmospheric and oceanic fluid dynamics. Altimetry-based estimates demonstrate that such patterns are non-stationary and do not span the entire zonal width of ocean basins. Modeling re- sults further suggest the key role of these zonally-elongated large-scale transients (ZELTs) in the anisotropic material transport in the ocean. In this study we investigate the mech- anisms of formation and maintenance of ZELTs in the ocean.

We demonstrate that dynamics of ZELTS is governed by transient non-linear forcing which has two parts: the part that is due to interactions between eddies and the part that is due to the scattering of eddies over the mean state. The importance of each of these terms is established by simulations with artificially modified non-linear forcing. In particular, the results indicate that neglecting the eddy-eddy interactions results in a complete disappearance of ZELTs.