Vertical Splitting of Vortices in Geophysical Dipoles

Abstract

The processes involved in the vertical splitting of vortices in geophysical dipoles, rotating and stably stratified, are investigated using a three-dimensional numerical model under the f-plane and Boussinesq approximations. Vertical splitting in asymmetric dipoles is possible when the vortices have a similar amount of potential vorticity but significantly differ in vertical extent. One representative case of vertical splitting is analyzed, and it is found that prior to the splitting there is a shearing period characterized by vertical unalignment and loss of horizontal axisymmetrization. The splitting starts when the upper and lower parts of the deep vortex independently experience vertical alignment and horizontal axisymmetrization. Vertical splitting also involves vortex horizontal splitting in the intermediate layers, which might explain the vertical asymmetry found in some isolated subsurface vortices in the ocean interior.