Ocean Currents: Factors Influencing and General Characteristics

Read this article to learn about the ocean currents: factors influencing and general characteristics of ocean currents! 

The ocean current is a general movement of a mass of water in a fairly defined direction over great distances.


Of all the movements in the oceanic water, ocean currents are the most important.

Warm Currents and Cold Currents:

There are two types of ocean currents. Warm currents are those which flow from the low latitudes in tropical zones towards the high latitudes in the temperate and sub-polar zones. Similarly, cold currents are those which flow from the high latitudes towards the low ones.

Factors Influencing Nature and Movement of Ocean Currents:

1. Factors related to the earth’s rotation:

Gravitational force and force of deflection.

2. Factors originating within the sea:


Atmospheric pressure, winds, precipitation, evaporation and insolation.

3. Factors originating within the sea:

Pressure gradient, temperature difference, salinity, density and melting of ice.

4. Factors modifying the ocean currents:


Direction and shape of the coast, seasonal variations and bottom topography.

General Characteristics of Ocean Currents:

These characteristics arise as a result of interplay of the above-mentioned factors and include the following:

1. The general movement of the currents in the northern hemisphere is clockwise and in the southern hemisphere, anti-clockwise (Fig. 3.7). This is due to the Coriolis force which is a deflective force and follows Ferrel’s law. A notable exception to this trend is seen in the northern part of the Indian Ocean where the current movement changes its direction in response to the seasonal change in the direction of monsoon winds.




4. Convergence along which the warm and cold currents meet and divergence from which they move out in different directions also control the currents.

5. The shape and position of coasts play an important role in guiding the direction of currents.

6. The currents flow not only at the surface but also below the sea surface. Such currents are caused by the differences in salinity and temperature. For instance, heavy surface water of the Mediterranean Sea sinks and flows westward past Gibraltar as a sub-surface current.

Given below is a survey of ocean currents in three major oceans.

General Direction of Moment Followed by Ocean Curents

Currents of the Pacific Ocean:

Under the influence of prevailing trade winds, the north equatorial current starts from the west coast of Central America and traverses a distance of 14,500 km moving from east to west before it turns northward off the Philippines to form the Kuroshio current (Fig. 3.8). From the south-east coast of Japan, under the influence of prevailing westerlies, the current turns eastwards and moves as the North-Pacific current, reaches the west coast of North America, and bifurcates into two.

The northern branch flows anti-clockwise along the coast of British Columbia and Alaska and is known as the Alaska current. The water of this current is relatively warm as compared to the surrounding waters in this zone. The southern branch of the current moves as a cold current along the west coast of USA and is known as the Californian current. The Californian current joins the north equatorial current to complete the circuit.

Also, there are two cold currents in the northern Pacific. Oyashio flows across the east coast of Kamchatka Peninsula to merge with the warmer waters of Kuroshio. The Okhotsk current flows past Sakhlain Islands to merge with the Oyashio current off Hokkaido.

Following the pattern in the northern hemisphere, the south equatorial current flows from east to west and turns southwards as the East Australian current. It then meets the South Pacific current near Tasmania which flows from west to east. Reaching the south-western coast of South America, it turns northward as the Peru Current. It is a cold current, which finally feeds the south equatorial current, thus completing the great circuit (Fig. 3.8)

Another current flows parallel to the north and south equatorial currents but in the opposite direction—from west to east. This current is known as the counter-equatorial current. The genesis of this current is explained by an upset in the water balance because of accumulation of water in the western sector due to movement of the two equatorial currents. The west to east flowing counter-equatorial currents maintain the water balance.

Map Showing Currents of the Pacific Ocean

Currents of the Atlantic Ocean:

As in the Pacific Ocean, the two equatorial currents move from east to west in northern and southern hemispheres and a counter-equatorial current flows from west to east. The south equatorial current bifurcates into two branches near Cape de Sao Roque (Brazil). Its northern branch reinforces the north equatorial current. Part of the combined current enters the Caribbean Sea and the Mexican Gulf, while the remainder passes along the eastern side of the West Indies as the Antilles current.

At this stage, there is a rise in water level in the Mexican Gulf, because of large amounts driven by trade winds and because of water brought by the Mississippi river. As a result, a current flows out through the Strait of Florida to be joined by the

Antilles current from the south. This combined current moves along the east coast of USA and is known as the Florida current upto the Cape Hatteras and as the Gulf Stream beyond that. From the Grand Banks, the Gulf Stream flows eastward across the Atlantic as the North Atlantic Drift. The main motive force for this current is supplied by the prevailing south-westerly winds (Fig. 3.9).

Map Showing Currents of the Atlantic Ocean

The North Atlantic Current breaks up into two branches on reaching the eastern part of the ocean. The main current, continuing as the North Atlantic Drift, reaches the British Isles from where it flows along the coast of Norway as the Norwegian current and enters the Arctic Ocean.

The southerly branch flows between Spain and Azores as the cold Canary current. This current finally joins the north equatorial current completing the circuit in the North Atlantic. The Sargasso Sea, lying within this circuit, is full of large quantities of seaweed.

The two cold currents—East Greenland current and the Labrador Current—flow from the Arctic Ocean into the Atlantic Ocean. The Labrador Current flows along part of the east coast of Canada and meets the warm Gulf Stream. The confluence of these two currents, one hot and the other cold, produce the famous fogs around Newfoundland. As a result of mixing of cold and warm waters, one of the world’s most important fishing grounds is created.

In the South Atlantic Ocean, the south equatorial current, flowing from east to west, splits into two branches near Cape de Sao Roque (Brazil). The northern branch joins the north equatorial current, whereas the southern branch turns southward and flows along the South American coast as the Brazil current.

The Brazil current swings eastward at about latitude 35°S to join the West Wind Drift flowing from west to east. A branch of the South Atlantic current flows along the west coast of South Africa as the cold Benguela current, which joins the south equatorial current to complete the circuit. Another cold current, the Falkland current, flows along the south-eastern coast of South America from south to north.

Currents of the Indian Ocean:

Being only half an ocean, completely landlocked in the north, the characteristic current circulation of the Indian Ocean is different from that of Atlantic or the Pacific Ocean. The currents in the northern portion of the Indian Ocean differ entirely from the general pattern of circulation. They change their direction from season to season in response to the seasonal rhythm of the monsoons. The effect of winds is comparatively more pronounced in the Indian Ocean.

In the northern section of the Indian Ocean, there is a clear reversal of currents between winter and summer. In winter, the north equatorial current and the south equatorial current flow from east to west. A counter-equatorial current flows from west to east, between the two equatorial currents.

The north-east monsoons drive the water along the coast of Bay of Bengal to circulate in an anti-clockwise direction. Similarly, along the coasts of the lands bordering the Arabian Sea, an anti­clockwise circulation of currents develops (Fig. 3.10).

Map Showing Patterns of Ocean Current Circulation in Different in the Indian Ocean

In summer, a strong current flow from west to east, which completely obliterates the north equatorial current during this season. It is due to the effects of the strong south-west monsoon and the absence of the north-east trades. There is no counter-equatorial current at this time of the year. Thus, the circulation of water in the northern part of the ocean is clockwise during this season.

The southern part of the Indian Ocean is less marked by the seasonal changes. The general pattern of circulation is simple and is anti­clockwise like that of the other southern oceans. The south equatorial current, partly led by the corresponding current of the Pacific Ocean, flows from east to west and thus, southward along the coast of Mozambique in Africa.

The current flowing through the Mozambique Channel is known as the warm Mozambique current. Further southward, the Mozambique current is joined by another branch of the south equatorial current flowing past Madagascar Island. After the confluence of these two streams, it is known as the Agulhas current. It still continues to be a warm current, till it merges with the West Wind Drift.

The West Wind Drift, flowing across the ocean in the higher latitudes from west to east, reaches the southern tip of the west coast, of Australia. One of the branches of this cold current turns northwards along the west coast of Australia. This current, known as the West Australian current, flows northward to feed the south equatorial current.

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