If surface winds are blowing from the south toward the north in the Northern Hemisphere, which way ...

When driven by the wind, the topmost layer of the ocean water in the Northern Hemisphere flows at about 45 to the right of the wind direction. The layer in the next layer down can feel the movement of the water immediately above. This deeper layer of water also moves at an angle to the right of the overlying water. The same thing happens in the layer below that, and the next layer, and so on, to a depth of about 100 meters (330 feet) at mid-latitudes. Each layer slides horizontally over the one beneath it with each lower layer moving at any angle slightly to the right of the one above. Because of frictional losses, each lower layer also moves more slowly than the layer above. The resulting situation is an Ekman spiral.



The net motion of the water down to about 100 meters (330 feet), after allowance for the summed effects of Ekman spiral (the sum of all the arrows indicating water direction in the affected layers), is known as Ekman transport. The direction of Ekman transport is 90 to the right in the Northern Hemisphere. Therefore, if winds are blowing from the south to the north, winds will be deflected 90 to the right, which would be toward the east.