Ekman Spiral
D1. Physical and chemical oceanography and marine meteorologyDefinition
Theoretical wind-driven current that rotates with depth due to Coriolis force.
The Ekman spiral is the idealized structure of wind-driven flow with depth in a homogeneous ocean: surface current sits 45 degrees to the right of the wind (Northern Hemisphere) and rotates clockwise while decaying exponentially over the Ekman depth. Integrating the spiral over depth gives the net Ekman transport at 90 degrees to the wind. Real spirals are flatter because turbulent eddy viscosity varies with depth and stratification caps the layer.