Ocean Eddies - Discover the 'Black Holes' of the Ocean

All the oceans of the world are full of unique phenomena. Oceanographers have been able to document the movement of ocean waters to indicate things like currents, weather, and more. Ocean eddies serve as one crucial piece to the big picture of understanding how the oceans work.

What is an Ocean Eddy?

Oceanographers document ocean currents, which include long, permanent features like the Gulf Stream and smaller, episodic water flows. Eddies in the ocean, by contrast, are temporary loops of swirling water. These eddies form as water spins away from surface currents thanks to a bend in the current that creates a loop. When formed, ocean eddies can travel many miles before dissipating. Smaller eddies might only last seconds, while scientists might document larger eddies for months or years. There are warm eddies and cold eddies, with cooler eddies more likely to capture nutrients and marine life.

Do not mistake eddies for gyres, which typically reach thousands of miles in diameter. Permanent ocean currents rim gyres. For example, there are five major gyres active around the world: the North and South Pacific Subtropical Gyres, the North and South Atlantic Subtropical Gyres, and the Indian Ocean Subtropical Gyre.

Ocean Eddies vs. Whirlpools

Although eddies may be used interchangeably with whirlpools by many people in conversation, they are two distinct scientific phenomena. Whirlpools are characterized by the movement of air or water around a central point. Whirlpools can be manmade but frequently occur in relation to extreme weather events, including hurricanes and thunderstorms.

Eddies occur when an object or change in direction obstructs a primary current. The result is circular motion in the opposite direction to the primary current. Eddies are typically larger and flatter than whirlpools.

Where Do They Occur in the World?

Eddies might occur in any of the world’s oceans, including small eddies that dissipate quickly. Many large ocean eddies, especially mesoscale eddies, occur in major ocean currents, including the Gulf Stream, the Kuroshio Current, and the Agulhas Current. The Gulf Stream originates in the Gulf of Mexico, heads up the eastern United States, and then into the Atlantic Ocean towards the northeast. The Kuroshio Current flows off the coast of Japan in the Pacific Ocean. The Agulhas Current is a boundary current on the Indian Ocean that flows south along Africa’s east coast. Eddies occurring off these and other currents move heat and nutrients throughout the world’s oceans.

Are Ocean Eddies Similar to Black Holes?

MIT reported how two researchers in 2013 likened the behavior of some massive ocean eddies to black holes. The rotating behavior of these water loops prevents water and other material from escaping, similar to how the photon sphere of a black hole traps light.

However, eddies do not perpetually trap water, nutrients, carbon, salt, and heat away from the rest of the ocean in the way black holes trap light. Instead, they play a vital role in regulating climate and transporting heat.

Why Are Ocean Eddies Important?

Eddies pump nutrients from high-nutrient regions near the equator to the center of other currents to feed phytoplankton. In turn, these phytoplankton serve as the base of a broad food chain, feeding sharks, turtles, and various types of fish.

Eddies can also provide unique opportunities for shipping companies to increase their speed if ships know where they might encounter them. However, ocean eddies can also slow down ships if they move around them in the wrong direction. Large and significant ocean eddies occasionally receive names from a U.S.-based company called Horizon Marine. The naming system is similar to hurricanes, with names following the alphabet, and helps to alert shipping companies to their presence along their routes.

Major ocean currents influence the weather, but smaller and more unpredictable eddies also impact climate in unforeseen ways. While the Gulf Stream famously blows warm air over Europe, the mesoscale eddies that form off the Gulf Stream are just as powerful when it comes to heat transfer. Oceanographers describe mesoscale eddies as an eddy between 6 and 300 miles in diameter that last as long as days or months. These mesoscale eddies separate off from turbulent currents like the Gulf Stream and hold immense amounts of kinetic energy. Ocean mesoscale eddies move heat toward the poles and also vertically to prevent excessive heat entering the deep ocean zones.

Impact of Climate Change on Eddy Development

Eddies have been called the weather of the ocean, which means climate change has had unusual effects on their formation and strength. Scientists have documented an energy increase in ocean eddies, with so far unknown impacts on the ability of the ocean to trap carbon. The intensification of ocean eddies has become an important area of research for scientists looking to predict climate change and future weather patterns.