Ekman transport

Ekman transport is the net movement of surface water driven by wind stress and deflected by Earth's rotation. In the idealized case, it flows 90 degrees to the wind.

Ekman spiral: A pattern in which current speed and direction change with depth under wind-driven, rotating flow. Its depth-varying currents explain how surface flow adds up to transport beneath the wind.
Coastal upwelling: The rise of deep water near a coast when surface water is transported offshore. Along some coasts, Ekman transport carries surface water away from shore and draws deeper water upward.
Coriolis parameter: The latitude-dependent quantity that measures the strength of Earth's rotational effect on horizontal motion. Its sign and magnitude determine the direction and strength of Ekman deflection.
Surface current: A horizontal flow of water near the ocean surface. Ekman transport describes the net movement of a surface layer, not every local surface current.
Coriolis effect: The apparent deflection of moving objects in a rotating reference frame. Earth's rotation turns wind-driven currents away from the direction of the wind.
Equatorial upwelling: The rise of deep water near the equator as surface waters move away from it. Opposing Ekman transports on either side of the equator diverge and draw deeper water upward.
Northern Hemisphere: The half of Earth north of the equator. Ekman transport is directed to the right of the wind in this hemisphere.
Wind-driven circulation: Ocean circulation caused by momentum transferred from winds to the sea surface. Ekman transport is one component of the broader circulation produced by winds.
Wind stress: The tangential force per unit area exerted by wind on a surface. It supplies the momentum that drives the ocean's surface layer.
Ekman pumping: Vertical motion driven by convergence or divergence in wind-driven surface transport. Changes in horizontal Ekman transport create vertical motion in the ocean interior.

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