Ekman Spiral in the Ocean

Steady wind stress on the ocean surface, Coriolis force, and vertical eddy viscosity A_z lead to the Ekman spiral: horizontal currents rotate and decay with depth on a scale δ = √(2A_z/|f|). Hodographs of (u, v) trace a logarithmic spiral; surface deflection relative to wind illustrates Ekman transport direction.

Who it's for: Physical oceanography or atmosphere boundary-layer introductions.

Key terms

  • Ekman spiral
  • Coriolis parameter
  • Eddy viscosity
  • Boundary layer

f = 2Ω sin(lat): sign controls spiral handedness; near the equator δ diverges — stay away from |lat| < 5° in this model.

Live graphs

How it works

Wind stress, Coriolis parameter, and vertical eddy viscosity set the Ekman depth and the turning of horizontal currents with depth — the classic spiral behind upwelling and ice-drift deflection.

Frequently asked questions

What happens near the equator?
f → 0 makes δ diverge; the model is not valid there—use mid-latitude settings.