What are the Directions in which the ocean moves?

Water in the ocean flows in two directions: horizontally and vertically. Currents are horizontal movements, while upwellings and downwellings are vertical changes.

What are the five major ocean currents?

The North Atlantic, South Atlantic, North Pacific, South Pacific, and Indian Ocean gyres are the five major ocean-wide gyres.

What is the biggest ocean current?

The Antarctic Circumpolar Current

What are warm ocean currents?

Warm currents are those that flow away from the equator and toward the poles or latitudes on the western side of ocean basins. They bring warm water to cold water areas and are mostly found on the eastern continents.

Ocean Currents, Map, Meaning, Types, Causes, Effects, Diagram

Table of Contents

Ocean Currents

A continuous general movement of ocean water in a specified direction is called an ocean current. These can be considered as a river running across the surface of the ocean.

Most surface currents carry water horizontally and vertically in the upper layer above the thermocline (you will learn about this later in this section). The water beneath the thermocline circulates as well, although at an extremely slow rate.

Based on these currents’ influence on the destination, they are classified as warm ocean currents and cold ocean currents. A warm stream is one that travels towards the pole in both hemispheres and transports warm water from lower to upper latitudes. A cold stream flows from the high latitudes to the tropics.

Ocean Currents Types

Ocean Currents are of the following types:

Based on Depth

Based on the depth, the ocean currents may be classified as surface currents and deep water currents:

Surface currents are those currents that circulate to a depth of 400m from the surface; they roughly constitute about 10 percent of all the water in the ocean.

Deepwater currents are caused due to changes in density and under the influence of gravity. They make up the other 90 percent of the ocean water.

The changes in the temperatures and salinity determine the density, which causes the vertical movement of water.

Deep waters sink into deep ocean basins at high latitudes when temperatures are cold enough to cause the density to rise.

Based on Temperature

Based on temperature, ocean currents are classified as cold currents and warm currents:

Cold currents transport cold water from high latitudes to low latitudes, bringing cold water into warm water areas. These currents are most commonly seen on the west coasts of continents at low and middle latitudes (in both hemispheres) and on the east coast at higher latitudes in the Northern Hemisphere.

Warm currents transport warm water from low to high latitudes and are most commonly seen on the east coasts of continents in the low and intermediate latitudes (true in both hemispheres). They can be found on the west coasts of continents at high latitudes in the northern hemisphere.

Ocean Currents Influence

1. Influence of Insolation

The water expands when heated by incoming solar radiation (insolation). As a result, the ocean water level at the equator is around 8 cm higher than in the middle latitudes. As a result, there is a minor gradient, and water flows down the slope.

2. Influence of Gravity

Gravity tends to pull the water down to pile and create gradient variation.

3. Influence of Temperature

Differences in the temperature of ocean waters at the equator and the poles influence the current movement. As warm water is lighter, it rises, and cold water is denser; it sinks. The warm equatorial waters move slowly along the surface towards the pole, while the heavier cold waters of the polar regions move along the bottom of the sea towards the equator.

4. Influence of Salinity

Based on the temperature, geographical area, the inflow of fresh water, etc., the salinity of ocean water varies from place to place. Waters of high salinity are denser than the waters of low salinity. Hence, high salinity waters sink and flow at the bottom towards low salinity waters. On the other hand, ocean waters of low salinity flow on the surface of ocean waters and move towards high salinity waters. For Example, in the partially enclosed Mediterranean Sea, there is a great difference in salinity between the waters of the open Atlantic Ocean and those of the Mediterranean Sea. The less saline water from the Atlantic Ocean flows into the Mediterranean Sea. However, this inflow is compensated by denser water that flows from the bottom of the Mediterranean to the Atlantic Ocean.

Influence Due to the Earth’s Rotation

Under the influence of the Coriolis force, the earth’s rotation deflects freely moving objects to the right, including ocean currents. This is a clockwise direction in the northern hemisphere (e.g., the direction of the Canaries and the Gulf Stream). It runs counter-clockwise in the southern hemisphere (for example, the Brazilian Current)

Influence of geographical Orientation: Crustal land masses block and affect the course of a current due to their geographical orientation. The Peruvian Current, for example, is formed when part of the West Wind Drift is diverted northwards by the tip of southern Chile.

Influence of the Trade Winds

The Trade Winds blow between the equator and the tropics, moving equatorial waters polewards and westwards and warming continents’ eastern shores. The North-East Trade Winds, for example, warm the southern and eastern shores of the United States by moving the North Equatorial Current and its derivatives, the Florida Current. The Westerlies blow in temperate latitudes.They result in a northeasterly movement of water in the northern hemisphere, driving the warm Gulf Stream to the western coast of Europe as the North Atlantic Drift. The westerlies are, however, less reliable than the ‘Trade Winds.’

The most significant effect on the flow of ocean currents is that of planetary winds. The North Indian Ocean has the best evidence of the prevailing winds’ impact on the current flows. The monsoon winds, which blow from the northeast during the winter and the southwest during the summer, completely modify the course of the currents.

Ocean Currents Atlantic Ocean

The North and South Equatorial Currents at the equator are constantly drifting from east to west under the influence of the consistent Trade Winds. The landmass in northeast Brazil splits the South Equatorial Current into the Cayenne Current, which flows down the coast of Guiana, and the Brazilian Current, which flows southwards along Brazil’s east coast.

The Cayenne Current is joined and reinforced by the North Equatorial Current in the North Atlantic Ocean, and it flows north-westward into the Caribbean Sea as a vast body of equatorial water. The Florida Current emerges from the Florida Strait between Florida and Cuba as part of the current entering Mexico’s Gulf. The balance of the equatorial water moves northeast of the Antilles, eventually joining the Gulf Stream off the coast of the United States of America. With a width of 35 to 100 miles, a depth of 2,000 feet, and a speed of three miles per hour, the Gulf Stream Drift is one of the most powerful ocean currents. The current follows the American coast and is subsequently redirected eastwards by the combined impact of the Westerlies and the earth’s rotation. The Gulf stream is known as the North Atlantic Drift as it gets to Europe. The warm equatorial water is carried to the European coasts by this current. The current branches in three directions from the North Atlantic: eastwards to Britain, northwards to the Arctic, and southwards along the Iberian coast.

According to oceanographic studies, about two-thirds of the water carried to the Arctic by the Gulf Stream is returned to the tropical latitudes each year as dense, cold Polar water that creeps southwards into the ocean bottoms. The Canaries Current, which flows southward, finally combines with the North Equatorial Current, completing the clockwise circuit in the North Atlantic Ocean.

There is no apparent current within this ring of currents in the centre of the Atlantic. This zone of negligible current leads to the formation of the Sargasso Sea. A massive amount of drifting seaweed forms the Sargasso Sea.

There are also currents that reach the North Atlantic from the Arctic areas, in addition to the clockwise circulation of the currents. The out-flowing arctic winds blow these chilly waters south. At the confluence point, the Irminger Current, which flows between Iceland and Greenland, cools the warm North Atlantic Drift. Between West Greenland and Baffin Island, the cold Labrador Current drifts south-eastwards until it meets the warm Gulf Stream off the coast of Newfoundland.

The circulation of the South Atlantic Ocean is similar to that of the North Atlantic Ocean. The circle is anti-clockwise, and the gathering of seaweed in the calm seas of the mid-South Atlantic is not as noticeable. At Cape Sao Roque, the South Equatorial Current splits into two branches, one heading south as the warm Brazilian Current. The pull of the prevailing Westerlies and the earth’s rotation accelerates the current eastwards, merging with the cold West Wind Drift as the South Atlantic Current. When the current reaches Africa’s west coast, it is rerouted northward as the frigid Benguela Current (the counterpart of the Canaries Current). It transports the West Wind Drift’s chilly polar waters to tropical latitudes. The Benguela Current rushes equatorward in a north-westerly direction, driven by the frequent South-East Trade Winds to join the South Equatorial Current. This completes the present circulation in the South Atlantic. The east-flowing Equatorial Counter Current lies between the North and South Equatorial Currents.

The circulation pattern in the Pacific is similar to that in the Atlantic, with some differences due to the Pacific’s larger size and more open nature. Correlate it to the Atlantic currents if you can.

Ocean Currents Indian Ocean

The South Indian Ocean’s currents form a circuit comparable to the Atlantic and Pacific Oceans. The Equatorial Current joins the West Wind Drift, which flows eastwards and turns equatorward as the West Australian Current, before turning southwards past Madagascar as the Agulhas or Mozambique Current.

Due to fluctuations in monsoon winds, the direction of currents in the North Indian Ocean completely reverses between summer and winter. During the summer, from June to October, when the South-West Monsoon is the dominating wind, the currents are blown south-westerly as the South-West Monsoon Drift.

This is reversed during the winter, commencing in December, when the North-East Monsoon Drift blows the currents from the northeast. The North Indian Ocean currents are the most striking example of the dominance of winds over ocean current circulation.