Ekman spiral
Velocity vectors at different depths trace out a spiral about a line perpendicular to water surface
- Wind-induced currents are 90°, 180° or more to wind direction
- Where flow is 180° to wind, velocity is ~4% of surface velocity
We say that the wind ‘penetrates’ to depth where flow is 180° to wind
Water above this depth of penetration is Ekman layer
Wind speed, water viscosity, & magnitude of Coriolis effect all affect depth to wind penetrates
Wind Generally penetrates to greater depths at low latitudes (except right at equator)