  We describe a stochastic variability mechanism which is genuinely internal to
the ocean, i.e. not due to fluctuations in atmospheric forcing. % The key
ingredient is the existence of closed contours of bottom topography surrounded
by a stirring region of enhanced eddy activity. This configuration leads to the
formation of a robust but highly variable vortex above the topography anomaly.
The vortex dynamics integrates the white noise forcing of oceanic eddies into a
red noise signal for the large scale volume transport of the vortex. The strong
interannual fluctuations of the transport of the Zapiola anticyclone ($\sim 100
\ Sv$) in the Argentine basin are argued to be partly due to such eddy-driven
stochastic variability, on the basis of a 310 years long simulation of a
comprehensive global ocean model run driven by a repeated-year forcing.
