This paper examines the stability properties of coastal
currents having the same potential vorticity (PV) structure but different
transports and widths. The PV structure is chosen so as to verify the Charney–Stern
necessary condition for instability: two PV fronts associated with opposite
sign gradients exist. The authors find that the characteristics of the eddies
formed by the current are sensitive to the transport and current width, and
very different vortex sizes can be obtained when varying the latter parameters.
The diameter is indeed shown to diminish when increasing the transport or
diminishing the current width. Analytical and numerical results also show
that there are parameter ranges for which the current is stable, and that
the Charney–Stern criterion is indeed not a sufficient condition for instability.
Large transports are, however, necessary to stabilize the current. The model
is then used to study the dynamics of a current subject to adiabatic changes,
and a few scenarios are reviewed. In particular, the authors explain how
eddies with different diameters can be generated from the same current.