What Is A Gyre?
A gyre is a series of ocean currents that move in a circular pattern. Winds formed as the earth spins and shifting wind patterns help create them.
The ocean gyre is not fixed to a certain location in the ocean but rather moves to correspond with wind patterns. They are known to power the “ocean conveyor belt,” which circulates ocean water across the world.
Gyres are created by three forces: the rotation of the Earth, wind patterns, and the landmasses of the Earth. The wind blows across the ocean’s surface, causing the water to move in the direction of the wind.
As part of the Coriolis effect, the earth’s rotation counteracts the movement of the wind.
The Coriolis effect deflects currents to the right in a clockwise motion in the Northern Hemisphere, whereas currents are deflected to the left in a counterclockwise motion in the Southern Hemisphere.
The Ekman spiral is created beneath the water’s surface by the Coriolis force.
When currents above the surface are deflected by 45 degrees, the Ekman spiral forms, while currents below the surface are deflected less as depth increases. The spiral design can drop to around 330 feet below the surface.
Do All Oceans Have Gyres?
Yes, all of the oceans on earth have at least one gyre. There are four named oceans: The Atlantic, Pacific, Indian, and Arctic.
In addition, there are 5 major gyres on Earth, these are the North Atlantic, the South Atlantic, the Indian, the North Pacific, and the South Pacific.
However, these are just the major gyres. Smaller gyres can occur in other bodies of water including rivers, lakes, and other basins. The Beaufort Gyre in the Arctic Ocean is an example of a smaller gyre.
The Beaufort Gyre is a massive swirl of water produced by high winds that force currents clockwise.
As Siberian and Canadian rivers drain into the Beaufort gyre, it contains relatively fresh water. Because of the comparatively freshwater, it contains, scientists have been consistently checking up on the Beaufort gyre.
When the winds die down and the gyre weakens, freshwater pours out and into the North Atlantic Ocean.
The infusion of freshwater from the Beaufort gyre, as well as freshwater from melting sea ice, may be contributing to the disruption of the ocean conveyor, a worldwide ocean current system.
What Current Flows Around the Center of Ocean Gyres?
The subtropical gyres are encircled by four linked currents: two boundary currents aligned roughly north-south at their eastern and western margins, and two east-west currents at the gyre’s northern and southern ends.
The positioning of the Earth’s landmasses, as well as the planet’s rotation, cause the boundary currents to be narrowest and deepest near the western border of the subtropical gyres.
Western boundary currents are also among the fastest non-tidal ocean currents on the planet, with speeds exceeding five miles per hour (2.5 meters per second) and carrying up to 100 times the combined flow of the world’s rivers.
The Gulf Stream in the North Atlantic, the Kuroshio in the North Pacific, and the Agulhas in the Indian Ocean are examples of these currents.
As the warm western border currents slow and spread, they turn east to produce the most poleward currents of their associated gyre.
They also serve as the southern boundary of the subpolar gyres in the north, allowing water to exchange between the subtropics and the Arctic.
Similarly, the Antarctic Circumpolar Current connects to the southern subtropical gyres via these currents in the south.
The slowest and most dispersed currents encircling the gyre are the cooler eastern border currents that travel from high latitudes toward the equator.
As they approach the equator, they head west and gain speed, propelled by trade winds and tropical sun.
Where Are the 5 Major Ocean Gyres?
There are five identified permanent oceanic gyre currents: the North Atlantic, the South Atlantic, the North Pacific, the South Pacific, and the Indian Ocean.
The center of the gyre zone in the middle of the North Atlantic, where currents ebb to practically nothing, is a long-known phenomenon since kelp and seaweed have congregated by the current in this location, giving it the name “Sargasso Sea.”
The South Atlantic Gyre is a subtropical gyre located in the southern Atlantic Ocean.
Northwesterly (or southeastward-flowing) winds drive eastward-flowing currents in the gyre’s southern section, which are difficult to differentiate from the northern boundary of the Antarctic Circumpolar Current.
This gyre encompasses the majority of the northern Pacific Ocean. It is the world’s largest ecosystem, spanning 20 million square kilometers and located between the equator and 50° N latitude.
The gyre is generated by four prevailing ocean currents that move in a clockwise round pattern:
To the north is the North Pacific Current, to the east is the California Current, to the south is the North Equatorial Current, and to the west is the Kuroshio Current.
The Southern Pacific Gyre is part of the Earth’s system of rotating ocean currents, and it is confined to the north by the Equator, to the west by Australia, to the south by the Antarctic Circumpolar Current, and to the east by South America.
The South Pacific Gyre’s center is the oceanic pole of inaccessibility, the location on Earth farthest from any continents or productive ocean basins.
The South Equatorial Current and the West Australian Current make up the Indian Ocean gyre.
The Indian Ocean gyre, which normally moves counter-clockwise, reverses direction in the winter due to the seasonal winds of the South Asian Monsoon.
Why Do Gyres Spin in Different Directions?
Gyres are primarily created by global wind patterns, and the Coriolis effect shifts the winds that affect the water 45o to form the gyres.
To the right, or clockwise, in the Northern Hemisphere, and to the left, or counterclockwise, in the Southern Hemisphere. The change in direction is caused mostly by changing wind patterns.
Why Do Ocean Gyres Exist?
The gyres exist because strong winds exert a mechanical force, or stress, on the oceans, causing the water to accelerate.
The imposed forces must be counteracted by frictional forces when the water rubs against the ocean bottom or side for the seas to be mechanically balanced.
Frictional forces only exist when the water is moving, therefore if the wind is blowing, the ocean must be moving, and an overall equilibrium between the wind and the frictional forces eventually occurs.
However, the rotation of the Earth has a significant impact on the structure of the gyres.
Large expanses of stagnant, calm water are circled by ocean gyres. Debris falls into these spots and, due to the lack of movement in the region, can pile up for years. These areas are known as garbage patches.
Significant garbage patches can be found in the Indian Ocean, the North Atlantic Ocean, and the North Pacific Ocean.
The North Pacific rubbish patch is also known as the Pacific trash vortex or the Great Pacific Garbage Patch.
The gyre’s circular motion attracts garbage, particularly small plastic particles. The debris eventually makes its way to the heart of the gyre, where it remains stuck and degrades into a kind of plastic soup.