Our magnificent ocean is one of the most sophisticated ecosystems on planet earth. There are a variety of intricate and interconnecting mechanisms taking place simultaneously to maintain harmony for the marine species who inhabit the ocean as well as for the human population who rely heavily on it. One of the many important systems within the ocean includes oceanic gyres, which we will be exploring further.
Oceanic gyres are a large system of circular currents formed by global wind patterns and forces created by the earth’s rotation. Gyres effectively appear and function as massive whirlpools or vortexes in the middle of the ocean. There are five major oceanic gyres (North Pacific, South Pacific, North Atlantic, South Atlantic, Indian Ocean) which fit into three subcategories (polar, subtropical, and tropical). Off the coast of California and right above the equator we have the subtropical North Pacific Gyre.
Image Credits: NOAA
The movement of the world’s major oceanic gyres helps drive the oceanic conveyor belt. The oceanic conveyor belt is responsible for circulating ocean water around the entire planet which in turn creates a constant circular motion within the ocean. This circulation of water is essential for regulating temperature, salinity, and nutrient flow.
Image Credits: NASA
There are three fundamental forces that cause the circulation of a gyre. To begin, earth’s continents and other landmasses such as islands create boundaries enabling the foundation and shape of oceanic gyres. Next, global wind patterns hold a great deal of strength that provides wind the power to drag on the ocean surface. This drag force triggers water to move in the direction that the wind is blowing. Finally, earth’s rotation deflects or changes the direction of the wind driven water flow. This deflection is part of the Coriolis effect.
The Coriolis effect is a mechanism continuously working throughout oceanic gyres. It is caused by the earth's rotation around its axis. This shifts surface currents by a measure of 45 degrees. In the northern hemisphere, ocean currents are deflected to the right in a clockwise motion. Whereas in the southern hemisphere, ocean currents are pushed to the left in a counterclockwise motion. A great small-scale example of this can be observed right in the comfort of your home! If you live in the northern hemisphere and you flush your toilet, you’ll notice the water will swirl clockwise. However, if you live in a country that’s located in the southern hemisphere such as Peru, you might notice that the same water moves counterclockwise.
Image Credits: NOAA
Surface currents physically drive the circulation of oceanic gyres. They are driven by wind that is fueled with energy from the sun and are responsible for transferring heat from the tropics to the polar regions and influencing global and local climate. In contrast, deep-ocean currents are driven by differences in water density which is controlled by a process known as thermohaline circulation. The word thermohaline refers to temperature (thermo) and salinity (haline). For instance, cold-dense-salty water will sink to the bottom of the ocean and warm-less-dense-salty water will float on top.
Beneath surface currents of a gyre, the Coriolis effect results in something called the Ekman spiral. Throughout this system, surface currents are deflected by about 45 degrees. Each deeper layer in the water column is deflected slightly less which results in a spiral pattern descending to about 300 feet. Due to wind having direct contact with the top layers of the water column the strength of the wind’s force is felt more immensely at the surface. As you travel deeper into the ocean that same force is felt at a lesser degree.
Image Credits: NOAA
The oceanic conveyor belt, earth’s rotation, global wind, surface currents, Coriolis effect and the Ekman spiral function together within the oceanic gyres to create and maintain the ocean’s environmental stability. To learn more about oceanic gyres and their impact on marine species and habitats go to https://www.ochabitats.org/livestreams to watch our new coffee and conservation presentation on gyres! Meanwhile, the next time we catch ourselves admiring the natural beauty of the ocean, we can also acknowledge the intrinsic value it rightfully holds.
Image Credits: Wendy Philip