beta spiral
From Glossary of Meteorology
In oceanography, the turning of the current vector that arises from stratified geostrophic flow when density is conserved following a parcel (as is approximately the case in the oceanic thermocline).
If θ is the angle of the current, U is its magnitude, f is the Coriolis parameter, g is the gravitational acceleration, and w is the vertical velocity, then ∂θ/∂z = -(gw/f'U2)(∂ρ/∂z), so that moving upward in the water column, currents will spiral clockwise in upwelling zones, and counterclockwise in downwelling zones.
