Two large warm water eddies are swirling to the north of the Gulf Stream current in this satellite image recorded with the AVHRR sensor (Advanced Very High Resolution Radiometer) aboard a NOAA satellite on June 11, 1997. Blue colors indicate cooler water, while yellow and orange colors indicate warmer water. Click on image for full size (192 Kb) Courtesy of the Ocean Remote Sensing Group, Johns Hopkins University Applied Physics Laboratory

Surface ocean currents move in predictable directions over time. However, on a smaller scale, the water in currents moves in complex and variable ways. And those complexities can cause some water to spin away from a current, creating an eddy.

The swirling water of an eddy can be more than 100 km (60 miles) in diameter. The center of some eddies is cool while the center of others is warm. Warm water eddies are usually nutrient poor and marine life is sparse in them. Cold water eddies are usually nutrient rich and full of life.

Eddies form when a bend in a surface ocean current elongates over time, making a loop. The loop separates from the main current to form the eddy. The Coriolis effect causes similar eddies to rotate in opposite directions in the different hemispheres so that in the north, cold water eddies rotate counterclockwise and warm water eddies rotate clockwise, while in the south, cold water eddies rotate clockwise and warm water eddies rotate counterclockwise. There is evidence that the topography of the ocean floor can help eddies to form too. Once an eddy forms, the swirling waters last for at least a few months.

The satellite image at the left of sea surface temperatures (SST) shows two large circular features above the Gulf Stream current in the Atlantic near the northeast coast of the United States. These are eddies. In this image, surface water is colored depending on its temperature with blues and purples for the coldest water and orange and yellow for warmer water. The orange color of these eddies indicates that they are warm water eddies. This area of the ocean – the Gulf Stream - tends to have some of the largest and most well defined eddies in the world.

Two large warm water eddies are swirling to the north of the Gulf Stream current in this satellite image recorded with the AVHRR sensor (Advanced Very High Resolution Radiometer) aboard a NOAA satellite on June 11, 1997. Blue colors indicate cooler water, while yellow and orange colors indicate warmer water. Click on image for full size (192 Kb) Courtesy of the Ocean Remote Sensing Group, Johns Hopkins University Applied Physics Laboratory

Sometimes water spins away from a surface ocean current, creating an eddy.

The swirling water of an eddy can be more than 100 km (60 miles) in diameter. The center of some eddies is cool while the center of others is warm. Marine life is sparse in warm water eddies, where the water does not have many nutrients. Cold water eddies are usually full of nutrients and marine life.

Eddies form when a bend in a surface ocean current lengthens and eventually makes a loop, which separates from the main current. The Coriolis effect causes cold water eddies to rotate counterclockwise and warm water eddies to rotate clockwise in the Northern Hemisphere while in the Southern Hemisphere cold water eddies rotate clockwise and warm water eddies rotate counterclockwise. There is evidence that the topography of the ocean floor can help eddies to form too. Once an eddy forms, the swirling waters last for at least a few months.

The satellite image at the left of sea surface temperatures (SST) shows two large circular features above the Gulf Stream current in the Atlantic near the northeast coast of the United States. These are eddies. In this image, surface water is colored depending on its temperature. Cooler water is shown with blue and purple and orange and yellow show warmer water. The orange color of these eddies means that they are warm water eddies. This area of the ocean – the Gulf Stream - tends to have some of the largest and most well defined eddies in the world.

Two large warm water eddies are swirling to the north of the Gulf Stream current in this satellite image. Blue colors show cooler water, while yellow and orange colors show warmer water. Click on image for full size (192 Kb) Courtesy of the Ocean Remote Sensing Group, Johns Hopkins University Applied Physics Laboratory

Sometimes water spins away from a surface ocean current. This makes an eddy.

The center of some eddies is cooler water while the center of others is warmer water. There isn’t as much marine life or as many nutrients in warm water eddies as there is in cold water eddies.

Eddies are made when a bend in a surface ocean current makes a loop that breaks away from the current. The Coriolis effect makes eddies to rotate in different directions in the different hemispheres. Cold water eddies to rotate counterclockwise and warm water eddies to rotate clockwise in the Northern Hemisphere. In the Southern Hemisphere it is just the opposite. Once an eddy forms, the swirling waters last for at least a few months.

The image at the left, taken from a satellite high in the sky, shows two large circles above the Gulf Stream current in the Atlantic Ocean. These are eddies. In this image, surface water is colored depending on its temperature. Cooler water is shown with blue and purple and orange and yellow show warmer water. The orange color of these eddies means that they are warm water eddies. The Gulf Stream can have some of the largest and most well defined eddies in the world.