Ocean Currents

Gravity, wind friction, and water density variations in different sections of the ocean form an ocean current, which is made up of horizontal and vertical components of the circulation system of ocean waters.

 Ocean currents, like winds in the atmosphere, transport considerable amounts of heat from Earth’s equatorial zones to the poles, and hence play an essential part in shaping coastal climates. Ocean currents and atmospheric circulation also have an impact on one another.

What is Ocean Current?

Gravity, wind (Coriolis Effect), and water density drive ocean currents, which are the continuous, predictable, directed movement of saltwater. Ocean water has the ability to move both horizontally and vertically. Up dwellings and down dwellings are terms for vertical movements, whereas currents are used to describe horizontal motions. This abiotic system is in charge of heat transport, biodiversity variations, and the Earth’s climate system.

Ocean Currents Types:

1) Currents at the Surface

Wind is the primary driver of these currents, which occur on the ocean’s upper layer. They have an impact on the water in the ocean’s upper 300 metres. The currents reflect the planet’s large-scale air circulation, which is largely caused by the sun’s uneven heating of the planet’s surface.

As a result, the currents generate gyres, which are rotating systems in the centre of ocean systems. On a global scale, surface currents are crucial for redistributing heat.

2) Deep-water Currents 

Deep-water currents occur deep within the ocean, as opposed to surface currents that occur on the ocean’s upper surface. They are not affected by the wind since they exist far below the surface.

They are, however, caused by variations in the density of ocean water and are influenced by the water’s temperature and salt content.

3) Currents that run vertically

Up dwelling currents are those that travel from deep inside the ocean to the surface. They are in charge of transporting organic stuff from the ocean’s depths to the surface.

For example, they help some marine species by sweeping nutrients upward. It can be seen when there are tremors or earthquakes on the ocean’s surface, causing the waves to rise.

4) Down dwelling

These are currents that transport material from the ocean’s surface to its depths. When currents converge or the ocean is driven against a coastline, surface water can be forced downwards by the pressure of the water.

It’s crucial because the breakdown of organic materials would quickly deplete the dissolved oxygen in the sediments and water below.

What causes the currents in the ocean?

Horizontal pressure-gradient forces, Coriolis forces, and frictional forces all play a role in causing and influencing ocean currents. Coriolis Force is mentioned in NCERT Notes on Factors Affecting Wind, which may be found in the linked article.

1. Solar heating

Water expands as a result of it. Around the equator, the water is around 8cm higher than in the middle latitudes. The water takes on a small incline and flows down the slopes. Warm water flows to the cold Polar Regions, whereas cold water travels to the warmer Equatorial Zones.

2. The wind

Ocean currents are caused by the wind, which pushes the water on the surface and causes the currents. Surface currents are caused by the wind, and they redistribute ocean water based on density and temperature.

3. Gravity

Gravity tends to drag objects towards the earth’s surface. When the wind blows over the ocean, the water piles up in the wind’s direction. As a result, against the pressure gradient, gravity draws the water down the ‘slope.’

4. The water’s salinity

When water travels to the poles, it becomes cold and freezes into ice, leaving a portion of the salt behind. It raises the salinity of the underlying water, making it denser. The colder, saltier, and denser water sinks to the ocean’s bottom, where it is replaced by surface water.

5. Temperature

Warm water tends to linger on the ocean’s surface. Up dwellings occur when denser, saltier, and cold water travels towards the equator, where it is warmer. The denser, saltier, and cold water heats up and becomes less dense, rising to the surface of the ocean.

6. Coriolis effect

It refers to the earth’s rotation. It exerts forces on all moving bodies in relation to the earth. The forces are strongest in the poles and least near the equator because the planet is spherical.

The wind changes direction as a result of the Coriolis effect, with Northern Hemisphere winds and currents travelling to the right and Southern Hemisphere currents deflecting to the left.

7. Earthquakes that occur underwater

They have the ability to cause ocean currents to move quantities of water inland. Earthquakes can also cause water-saturated sediments to migrate down slope, resulting in strong turbidity currents.

North and South Equatorial Currents:

Equatorial Current to the North

• Equatorial North In the Pacific and Atlantic Oceans, currents run from east to west.

• Equatorial North Between the latitudes of 10 and 20 degrees north, currents flow.

• It doesn’t have a connection to the equator.

Equatorial Current to the South

• It circulates through the Pacific, Atlantic, and Indian oceans.

• From east to west, the south equatorial current flows.

• Current flows are found between the equator and 20 degrees south latitude.

Conclusion

Ocean currents, which work like a conveyor belt, transport warm water and precipitation from the equator to the poles and cold water from the poles back to the tropics. Ocean currents thus help to regulate global climate by balancing the uneven distribution of solar radiation reaching the surface of the Earth.