Evolution of isolated vortices in a rotating fluid of finite depth

Laboratory experiments have shown that monopolar isolated vortices in a rot ating flow undergo instabilities that result in the formation of multipolar vortex states such as dipoles and tripoles. In some cases the instability is entirely two-dimensional, with the vortices taking the form of vortex co lumns aligned along the direction of the ambient rotation at all times. In other cases, the vortex first passes through a highly turbulent three-dimen sional state before eventually reorganizing into vortex columns. Through a series of three-dimensional numerical simulations, the roles that centrifug al instability, barotropic instability, and the bottom Ekman boundary layer play in these instabilities are investigated. Evidence is presented that t he centrifugal instability can trigger the barotropic instabilities by the enhancement of vorticity gradients. It is shown that the bottom Ekman layer is not essential to these instabilities but can strongly modify their evol ution.