Understanding the eddies

We are south of the Canary Islands to study eddies, which are a phenomenon that consists of circular currents of water propagating throughout the ocean, altering the environment in their path. There are 2 main types of eddies depending on the rotation: cyclonic eddies rotate anticlockwise and anticyclonic eddies rotate clockwise, in the northern hemisphere. Consequently, each type of eddy affects the environment in a way.

But, how are they formed? The Canary Islands are affected by the Canary Current, which flows from the Portuguese coast to Cabo Blanco, being a very energetic current. When it meets the islands, it can be disturbed and suffer deviations, giving rise to eddies in the leeward areas.

The formation of eddies is explained by the influence of the Coriolis force. Since the ocean is a fluid located in a rotating system, such as the Earth, the movement that occurs in the ocean is affected by this rotation, producing the Coriolis effect. Therefore, sea currents and water masses that move in the northern hemisphere suffer a deviation of 90º to the right, and those that move in the southern hemisphere 90º to the left.

In the northern hemisphere, when the eddy is cyclonic, the Coriolis force acts outward, producing a vacuum in the center that causes a rise in deep water. Consequently, the centers of these eddies have a low temperature and a high concentration of nutrients. On the contrary, when the eddy is anticyclonic, the force acts towards the center piling up water, which produces a sinking towards the depths. In these eddies the center has similar properties to the surrounding surface waters, with few nutrients and higher temperatures.