Meridional Motion of Mixing Eddies

Abstract

A two-layer model of anticyclonic eddy propagation including the effects of diapycnal mixing is presented. The lower layer is assumed to be of finite volume, whereas the upper layer is infinite in horizontal extent, and its dynamics are quasigeostrophic and wavelike. Integral expressions for the zonal and meridional velocity am obtained using center of mass calculations. The meridional motion is a result of both southward and northward velocities in the upper layer generated by Sverdrup forcing due to diapycnal mixing and stretching of vortex lines by the collapsing eddy. Net meridional motion of the eddy arises by requiring the mixing eddy to collapse both vertically and horizontally as it adjusts cyclostrophically. Moreover, it is shown for anticyclones in solid body rotation such motion must be equatorward. The specific case of a parabolic eddy is used to illustrate the theory, and application is made to Mediterranean salt lenses and warm core rings.