Ekman transport describes the net movement of water produced when wind transfers momentum to the ocean surface. It is a key part of wind-driven circulation and helps explain why surface water does not move exactly in the direction of the wind.
Wind exerts a frictional force, or wind stress, on the ocean surface. This force transfers momentum to the upper part of the water column, often described as roughly the upper 10–100 meters. The moving surface water then drags water beneath it through internal friction and turbulent mixing.
All flashcards
What is Ekman transport?
The net movement of water through the wind-driven Ekman layer, deflected by Earth's rotation from the wind direction.
What is wind stress?
The frictional force by which wind transfers momentum to the ocean surface.
Which way does Coriolis deflection act in each hemisphere?
It deflects moving water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
How do surface current and net transport angles differ?
In the idealized model, surface current is about 45° from the wind, while integrated transport is about 90° from the wind.
What did Nansen observe during the Fram expedition?
He noticed that Arctic ice drifted at an angle to the wind, an observation later explained by Ekman.
Quiz questions
What vertical motion is associated with divergence of surface water in the Ekman framework?Answer: Water rises to replace it, a process called Ekman suction.
When Ekman transport carries surface water away from a coastline, what typically happens?Answer: Deeper water rises toward the surface as coastal upwelling.
What assumption does the classic Ekman derivation make about vertical eddy viscosity?Answer: It remains constant with depth.
In the idealized Ekman depth scale, which change tends to make the layer deeper?Answer: Greater vertical eddy diffusivity.
How can upwelling support productive marine ecosystems?Answer: It brings nutrients into the sunlit layer, supporting phytoplankton growth.
Based on the Wikipedia article Ekman transport, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.