Circulation of the ocean water

Introduction

The Atlantic Ocean is the second largest ocean in the world, stretching from the Northern Hemisphere to the Southern Hemisphere. It covers approximately one-fifth of the earth’s surface. Currents of the Atlantic Ocean play a significant role in influencing the climates of North-Western Europe and North-Western Africa. The currents are also instrumental in preserving the fishing grounds in the Grand Banks off Newfoundland, Canada, which is one of the richest fishing grounds on the earth.

Ocean Currents: Atlantic Ocean

Ocean currents represent the movement of a regular volume of water in a definite path and direction. Ocean currents are influenced by certain factors such as: 

• Heating by solar energy leads to the expansion of water

• Wind blowing on the surface of the ocean and propelling the movement of water

• The force of gravity draws the water inward and creates variation in gradient

• The effect of the Coriolis force causes the water to move to the left in the Southern Hemisphere and to the right in the Northern Hemisphere 

All these factors impact the ocean currents in the Atlantic Ocean. The currents marking this gigantic water body are the Equatorial Atlantic Ocean currents, South Atlantic Ocean currents, and North Atlantic Ocean currents.

Equatorial Atlantic Ocean Currents

The Easterly Trade Winds in the region constantly drifts two currents from east to west called North Equatorial current and South Equatorial current originating from the west coast of Africa. An east-ward flowing equatorial counter-current flows between the two equatorial currents. Due to their proximity to the equator, these are all warm currents. There are 3  in the equatorial region. These are:

North Equatorial Current: This equatorial current is normally formed between the equator and 10° N latitude. The upwelling of cold water around the west coast of Africa causes the formation of this current. The general movement of this warm current is from east to west but is deflected towards the north while crossing the mid-Atlantic Ridge near 15°N latitude and then turns southwards. The land barrier of the east coast of Brazil bifurcates the current into the Antilles current and Caribbean current.

South Equatorial Current: This warm current flows between the equator and 20° S latitude, moving from the western coast of Africa to the eastern coast of South America. Once the current hits the east coast of Brazil, it bifurcates into two branches. One moves northwards and merges with the north equatorial current near Trinidad. The other runs southwards, parallel to the east coast of South America.

Counter Equatorial Current: The current flows westward, between the strong north and south equatorial currents. The drift is stronger in the east, known as the Guinea Stream. It is marked by a relatively higher tempera­ture and lower density than the two equatorial currents.

North Atlantic Ocean Currents

The trade winds in the North Atlantic are instrumental in maintaining steady east to west currents. The major ocean currents in the Atlantic Ocean in the Northern Hemisphere are:

Gulf Stream: This is a system of several currents and is named Gulf Stream because it originates in the Mexican gulf around 20° N latitude. Its north-easterly movement along the eastern coast of North America continues till it reaches the western coasts of Europe around 70° N latitude. This current system comprises:

• Florida Current originates from the strait of Florida and runs up to Cape Hatteras
• Gulf Stream originates from Cape Hatteras and moves towards Grand Bank
• The North Atlantic Drift moves from Grand Bank to the coast of Western Europe

Canaries Current: This current brings cold water from the higher latitudes of the polar region. It is the continuation of the North Atlantic Drift flowing south along the coast of the Canary Islands after turning southward near the Spanish coast. The cold current lowers the otherwise hot temperatures of the western coast of North Africa between Madeira and Cape Verde, where it flows at an average velocity of 8 to 30 nautical miles per day.

Labrador Current: This cold current originating in the Baffin Bay and the Davis Strait off the coast of Greenland flows along the coast of Newfoundland and Grand Banks. It brings large icebergs to this region, causing problems to navigate through the ocean. Around 50°W longitude, it merges with the warm Gulf Stream near Newfoundland, producing dense fog.

South Atlantic Ocean Currents

The pattern in which the South Atlantic Ocean flows is similar to the North Atlantic Ocean but in the counterclockwise direction. There are 4 major Ocean Currents in the Southern Hemisphere. These have been discussed below: 

• Falkland Current: This current brings in cold water from the Antarctic Sea. It flows from the south to the north, along the east coast of South America, up to Argentina. The current is at its most powerful state around 30⁰S latitude. It brings along icebergs to the South American coast from the Antarctic region

• Brazilian Current: This warm current formed by the bifurcation of the South Equatorial Current at Cape Sao Roque in Northeast Brazil is highly saline. It flows southward along the east coast of South America up to 40°S latitude. It is then deflected towards the east by the impact of the Westerlies and the rotation of the earth. It merges with the cold Falkland current, coming from the south under 40°S latitude

• South Atlantic Drift: Also known as the Westerlies Drift, it is the eastward continuation of the Brazil current. The deflection of the southward moving Brazil current to the east is caused by the Westerlies and hence the name Westerlies Drift. This cold current is also known as the Antarctic Drift

• Benguela Current: When the South Atlantic Drift bifurcates at the southern tip of Africa, a branch of the drift flows along the west coast of South Africa. This is known as the cold Benguela current, and it eventually joins the south equatorial current to complete this circuit of the ocean currents

Conclusion

The ten major currents of the Atlantic Ocean have been discussed here. Their origin, the factors that influence their movements, and the paths along which they flow have been pointed out. In addition to this topic, it is also important to study the ocean currents of the Pacific and Indian oceans to get a holistic understanding of how they operate and the impact they have on the climate systems.