DETAILED NOTE ON EKMAN SPIRAL AND RELATION WITH CORRIOLIS FORCE

EKMAN SPIRAL

1. Ekman Spiral

2. Ekman Spiral   The Ekman spiral, named after Swedish scientist Vagn Walfrid Ekman (1874-1954) who first theorized it in 1902, is a spiral pattern of ocean currents caused by the Coriolis effect. When surface water molecules move by the force of the wind, they, in turn, drag deeper layers of water molecules below them. The result is that each layer of water moves more slowly to the right or left, creating a spiral effect. The flow of a mass of water actually occurs as a series of sheet like movements called laminar flow.

3.   As each layer of water begins to move, a frictional drag occurs on the water molecules immediately below the surface layer. This drag produces a turbulent flow with irregular eddies. The motion of each layer is slightly to the right of the one above. A series of spiral motion results, rather like a spiral staircase, with each step slightly to the right of the preceding one.

4. Because the deeper layers of water move more slowly than the shallower layers, they tend to “twist around” and flow opposite to the surface current. The total net diagram has been called the Ekman spiral a model developed to describe the total movement through the mass of water. 1. The wind 2. The drag force on the water 3. The direction of the water flow 4. The Coriolis Force

5. Coriolis Force & Ekman spiral The Coriolis effect causes surface water to move to the right of the wind in the Northern Hemisphere and to the left in the Southern Hemisphere. Like surface water, the deeper water is deflected by the Coriolis effect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

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