Pt. Shaw, A NUMERICAL-SIMULATION OF THE EVOLUTION AND PROPAGATION OF GULF-STREAM WARM-CORE RINGS, Journal of physical oceanography, 24(3), 1994, pp. 573-586
The evolution and propagation of Gulf Stream warm core rings in a flat
-bottom, beta-plane ocean are studied using a three-dimensional primit
ive equation model. Rings are produced by a heat source that is turned
on and off slowly in the upper 750 m of the water column. Besides an
anticyclone in the upper ocean, a deep cyclone is generated below the
surface eddy. In the first 30 days, the surface anticyclone moves slow
ly southwestward because of beta dispersion and vorticity advection. I
n waters 4000 m deep, both the anticyclone and the cyclone intensify,
and a barotropic vortex pair is formed. The vortex pair moves rapidly
southeastward. Its propagation becomes steady and eastward after the c
yclone sheds an eddy. The cyclone in the vortex pair moves away from t
he ring at the end of 6 months, and both vortices begin to propagate w
estward separately. Fluid to a depth of 3000 m, much deeper than that
of forcing, is transported by the ring. The formation of a strong vort
ex pair is associated with the generation of relative vorticity in bot
h vortices by unstable waves of the second azimuthal mode. In strong r
ings, the increase in vorticity could produce rapid propagation. Eastw
ard propagation is a result of change in planetary vorticity and loss
of relative vorticity during cyclone splitting. In waters shallower th
an 4000 m, the vortex pair is less stable and more vorticity is lost b
y cyclone splitting. There is still a rapid movement toward the south
but the eastward propagation is weak. Rings in waters shallower than 4
000 m are likely to remain on the continental slope off the U.S. East
Coast and induce large amounts of momentum and mass transfer over the
continental margin.