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Geography Oceanography, and Weather

Ocean Currents

What is an Ekman spiral?

Vagn Walfrid Ekman (1874–1954), a Swedish physicist and oceanographer, discovered that a combination of the Coriolis effect, the movement of surface waters, and the friction caused by winds blowing on the ocean’s surface have an influence on current direction. In the Northern Hemisphere, the end result is that currents will be pushed to the right, and in the South the opposite occurs, forming spirals like weak whirlpools in the water. The effect, however, penetrates the ocean’s surface only to a degree (the null point), as the influence of these factors weakens with water depth. (The layer affected by the spiral is called the Ekman layer). Scientists have noted that the Ekman spiral is most obvious underneath sea ice, because waves and other forces in the open sea nearly cancel out the effect. However, the Ekman spiral also applies to the Earth’s atmosphere, where they are seen in surface winds.



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