Ageostrophy
Ageostrophy is the real condition that works against geostrophic wind or geostrophic currents in the ocean, and works against an exact balance between the Coriolis force and the pressure gradient force. While geostrophic currents or winds come from an equilibrium of a particular system, ageostrophy is more often observed because of other forces such as friction or the centrifugal force from curved fluid flow.
