August 12, 2013 - Cyclonic eddies north of Sicily
The world’s oceans are in constant motion, moving from one area of Earth to another in broad sweeping gyres, creating the flow of what is known as the global conveyor belt, which plays a large part in determining the climate in many regions of Earth. Not all ocean motion is on such a grand scale, however. Local forces can cause turbulence in the flow of water, and this turbulence can create a large variety of patterns, some of which can be seen from space.
On July 19, 2013 the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite flew over Sicily and captured this true-color image of turbulent water just north of the island.
On Sicily’s northwest coast, the city of Palermo sits on the edge of the crescent shaped Gulf of Palermo. This large city, which boasts a 2,700 year history, can be seen as a gray smudge. Just off the eastern tip of the Gulf of Palermo an onion-like series of concentric circles appears in the waters of the Tyrrhenian Sea.
Known as a “cyclonic eddy” in the northern hemisphere, this turbulence is created when cooler water from deep in the ocean moves upward, causing surface water to move away from the upwelling center and rotate in a counter clockwise direction. The center of the cyclonic eddy is likely cooler than, and slightly lower than, the surrounding surface water. Such upwellings bring nutrients from deep in the ocean towards the surface, and often are areas of robust growth of marine life.
At least two other circular areas of turbulence can be seen in this image. Both are located northeastward from the first, in the direction of the Aeolian Islands. Both of these swirls are also associated with other apparent turbulence, and may be eddies created from water flowing around the islands, especially the one closest to the southern part of the island chain.