Maarg Manthan · Topic 6.10

Major Ocean Currents of the World and Their Effects

Geography › Oceanography · Topic 6.10

The major ocean currents follow the large circular gyres of each ocean. In the Pacific and Atlantic, warm currents such as the Kuroshio, the Gulf Stream and the North Atlantic Drift carry heat from the tropics to higher latitudes, and cold currents such as the Humboldt (Peru), the California, the Canary and the Benguela return towards the equator. In the northern Indian Ocean the currents reverse with the monsoon. Currents affect climate, rainfall, fishing, shipping and the spread of marine pollution.

11 min read · UPSC Prelims · Geography · Oceanography

At a Glance

Warm currents Gulf Stream, Kuroshio, Brazil, Agulhas
Cold currents Humboldt, California, Canary, Benguela
Monsoon drift Northern Indian Ocean
Climate effect Warms or cools coasts
Fishing Cold current meets warm
Exam link UPSC Prelims, Geography: Oceanography

Where Does It Fit?

This topic follows the general account of ocean currents and names the important currents in each ocean. It also ties them to the climate, which is a recurring theme in the physical geography of India and the world. Previous topic: Tides: Tidal Currents, Types and Importance. Next topic: Atlantic Meridional Overturning Circulation (AMOC).

What Are the Currents of the Pacific Ocean?

In short: each Pacific gyre has a warm western arm and a cold eastern arm, with an eastward countercurrent between them.

Current	Nature	Direction and location
North Equatorial Current	Warm	Flows west along about 10 to 15 degrees north, driven by the northeast trades
Kuroshio Current	Warm	Flows northeast along the east coast of Taiwan and Japan; the Pacific equivalent of the Gulf Stream
North Pacific Drift	Cool to warm	Flows east across the North Pacific in the westerlies
Alaska Current	Warm	Flows northwest along the coast of Canada and Alaska; keeps ports ice-free
California Current	Cold	Flows south along the west coast of North America; causes fog and a dry coast
Oyashio (Kamchatka) Current	Cold	Flows south from the Bering Sea along the Kamchatka and Japan coast; meets the Kuroshio and creates fog and rich fisheries
Equatorial Countercurrent	Warm	Flows east between the north and south equatorial currents at about 5 to 10 degrees north
South Equatorial Current	Warm	Flows west south of the equator
East Australian Current	Warm	Flows south along the coast of Australia
Peru (Humboldt) Current	Cold	Flows north along the coast of Chile and Peru; strong upwelling, rich fishery, desert coast; weakens in El Niño years, as in El Niño and La Niña: ENSO and the Indian Ocean Dipole Effect
Antarctic Circumpolar Current (West Wind Drift)	Cold	Flows east around Antarctica; the largest current in the world, joining the three oceans

Below the surface, the Equatorial Undercurrent or Cromwell Current flows eastward along the equator in the Pacific, at a depth of about 100 m, and brings water to the Galápagos.

What Are the Currents of the Atlantic Ocean?

Current	Nature	Direction and location
North Equatorial Current	Warm	Flows west and feeds the Caribbean and the Gulf Stream
Gulf Stream	Warm	Flows from the Gulf of Mexico through the Florida Current along the US east coast to about 40 degrees north, where it joins the North Atlantic Drift
North Atlantic Drift	Warm	Flows northeast toward Europe, warming the winters of northwestern Europe and keeping Norwegian ports open in winter
Canary Current	Cold	Flows south along northwestern Africa; completes the gyre
Labrador Current	Cold	Flows south from the Arctic along Canada; meets the Gulf Stream at the Grand Banks to cause fog; carries icebergs
East Greenland and Irminger currents	Cold and warm	Flow along Greenland; the Irminger is a branch of the North Atlantic Drift
South Equatorial Current	Warm	Flows west and divides at Cape São Roque in Brazil into a northern branch and the Brazil Current
Brazil Current	Warm	Flows south along the coast of Brazil
Falkland (Malvinas) Current	Cold	Flows north along Argentina
Benguela Current	Cold	Flows north along southwest Africa; creates the Namib desert and rich fishing
Guinea Current	Warm	Flows east in the Gulf of Guinea; the extension of the countercurrent
West Wind Drift	Cold	Flows east at 40 to 60 degrees south

The Gulf Stream system is shown in The Atlantic Ocean, where the circulation, the AMOC, is also described.

How Can You Remember the Pattern?

Warm on the west, cold on the east: in the tropics and the subtropics, the poleward currents on the western side of an ocean are warm (Kuroshio, Gulf Stream, East Australian, Brazil) and the equatorward currents on the eastern side are cold (California, Peru, Canary, Benguela).
Gyre direction: clockwise in the north, anticlockwise in the south.
Where warm meets cold: fog and fisheries, at the Grand Banks (Gulf Stream and Labrador) and off Japan (Kuroshio and Oyashio).
Cold currents and deserts: the Peru, Benguela, California and Canary currents lie beside the Atacama, Namib, Sonoran-Baja and Sahara coasts, as in World Climate Types (Köppen Classification): Equatorial, Monsoon, Savanna, Desert, Mediterranean, Temperate and Polar Climates.

As an analytical point, current maps are one of the commonest map-based questions, and the way to answer them is to link each current to its oceanic gyre and its coast, and not to learn names in isolation.

Why Do the Currents of the Northern Indian Ocean Reverse?

In short: the monsoon winds reverse twice a year, and the surface currents in the northern Indian Ocean follow them.

Unlike the Pacific and the Atlantic, the northern Indian Ocean is closed by the Asian landmass, and the winds there are the monsoon winds. The seasonal reversal of the winds therefore reverses the surface circulation, which is called the monsoon drift.

Season	Wind	Circulation in the north Indian Ocean
Summer (June to September)	Southwest monsoon	Clockwise: the southwesterly Monsoon Current flows east across the Arabian Sea and the Bay of Bengal; the Somali Current flows north along the African coast; the East Indian Coastal Current flows north along India’s east coast
Winter (December to February)	Northeast monsoon	Anticlockwise: the Northeast Monsoon Current flows west; the Somali Current flows south; the East Indian Coastal Current flows south along India’s east coast

The Equatorial Countercurrent, which is a permanent feature of the other oceans, exists here only in winter, when it flows east between the equator and about 8 degrees south, because the southwest monsoon in summer replaces it. The seasonal pattern was well known to ancient mariners, who used the monsoon winds and currents for trade between Arabia, India and East Africa.

What Is Special About the Somali Current?

Speed: in summer, the Somali Current is one of the fastest ocean currents in the world, with speeds of more than 2 m per second, and acts as a western boundary current in the northern Indian Ocean. It forms in a few weeks after the monsoon onset.
Upwelling: the southwest wind blowing parallel to the coast of Somalia and Arabia pushes surface water offshore by Ekman transport, so cold, nutrient-rich water comes up. Sea surface temperatures fall by several degrees, and productivity is very high, with rich fisheries in the western Arabian Sea, as in Ocean Currents: Horizontal and Vertical Motion; Cold and Warm Currents.
Monsoon link: the cool upwelled water reduces local evaporation, and the low-level Somali jet, the Findlater jet, carries moisture over the Arabian Sea to India, as in tropopause Minimum speed Roughly 110 km per hour Polar front jet…">Jet Streams: Permanent and Temporary Types and Their Impact on Weather.
Winter reversal: the current runs south, and the coast has weak upwelling.

What Are the Permanent Currents South of the Equator?

Current	Nature	Description
South Equatorial Current	Warm	Flows west across the ocean at about 10 degrees south, driven by the southeast trades; divides near Madagascar
Mozambique and Madagascar currents	Warm	Branches that flow south along the African coast and the east coast of Madagascar
Agulhas Current	Warm	A strong, narrow western boundary current flowing south-west along the east coast of Africa, similar to the Gulf Stream; it meets the westerlies off South Africa and turns back eastward, shedding warm rings into the Atlantic
West Wind Drift	Cold	Part of the Antarctic Circumpolar Current flowing east in the south
West Australian Current	Cold	Flows north along the west coast of Australia, completing the gyre; contributes to the aridity of the coast
Leeuwin Current	Warm	Flows south along the west coast of Australia, against the usual pattern for west coasts; carried by the Indonesian Throughflow and supports unusual corals at high latitude

The Indonesian Throughflow is the passage of Pacific water through the Indonesian seas into the Indian Ocean. It is the only low-latitude link between two oceans, and it transfers heat and fresh water, which affects the Indian Ocean Dipole and the monsoon, as in El Niño and La Niña: ENSO and the Indian Ocean Dipole Effect. As an analytical point, the Indian Ocean current system is the best example of how ocean circulation is organised by the atmosphere, and the way it reverses is a test of the monsoon theory. The ocean is also warming fast, and marine heatwaves in the western Indian Ocean are reducing fish catches and bleaching corals.

How Do Ocean Currents Affect Climate?

In short: a warm current warms and wets the air above it, and a cold current cools and dries it.

Effect	Mechanism	Examples
Warmer coasts in high latitudes	Warm currents carry heat poleward and warm the winds that blow over them	The Gulf Stream and North Atlantic Drift keep northwestern Europe and the ports of Norway ice-free in winter; the Alaska Current warms the coast of Alaska; Britain is much warmer than Labrador at the same latitude
Cooler tropical coasts	Cold currents cool the air along western coasts	Peru, Benguela and Canary currents lower coastal temperatures; Lima and Walvis Bay are cooler than other places at the same latitude
Rainfall	Warm currents increase evaporation, humidity and rain on the east coasts; cold currents stabilise the air and prevent rain	Rain along the east coasts of Brazil, Florida and Japan; the dry coasts of Atacama, Namib and Baja California
Deserts	Cold currents and onshore winds give fog but no rain	The Atacama, Namib and the coastal Sahara; the Atacama is among the driest places on Earth
Fog	Warm moist air cooled by a cold current to its dew point	Fog at the Grand Banks where the Gulf Stream meets the Labrador Current; the summer fog of San Francisco over the California Current; the fogs of the Kuril coast, as in Types of Clouds: Cirrus, Cumulus, Stratus, Nimbus and Their Combinations
Cyclones and monsoon	Warm seas feed tropical cyclones; ocean heat influences monsoon rain	Typhoons over the Kuroshio region; the heat in the Arabian Sea and Bay of Bengal, as in Tropical Cyclones: Formation Conditions, Paths, Naming Conventions, Early Warning Systems

Currents also drive climate cycles. The weakening of the Peru Current in El Niño changes weather across the world, as in El Niño and La Niña: ENSO and the Indian Ocean Dipole Effect, and the large-scale circulation moves a major share of the heat from the equator to the poles, along with the atmosphere, as in Heat Balance of the Atmosphere: Conduction, Convection, Advection, Terrestrial Radiation, Albedo.

How Do Currents Affect Fishing and Marine Life?

Plankton and food chains: where a warm and a cold current meet, or where deep cold water comes to the surface by upwelling, nutrients reach the sunlit layer and plankton bloom. This is the base of the food chain.
Major fishing grounds: the Grand Banks (Gulf Stream and Labrador), the seas around Japan (Kuroshio and Oyashio), the Peruvian coast (Peru Current), the North Sea, the coast of Namibia and South Africa (Benguela) and the Somali-Arabian coast (summer upwelling) are the world’s best fishing grounds, as in Persian Gulf Largest sea Philippine Sea or South China Sea by area…">Major Gulfs, Bays and Seas of the World.
Larval and species dispersal: currents transport the eggs and larvae of fish, corals and eels over long distances, such as the eels of the Sargasso Sea, which cross the Atlantic with the Gulf Stream.
Warm-water intrusions: in El Niño years, the Peruvian anchovy collapses as the cold, rich upwelling is replaced by warm water. The marine heatwaves are now affecting the distribution of fish stocks, and fishing communities, including those of India, are seeing the shift of the catch.

Why Is This Topic Important?

Map-based Matching questions
Pattern Gyre logic
Application Deserts and fisheries

What Came Next?

The next topic describes the Atlantic Meridional Overturning Circulation, the deep-ocean part of the Atlantic current system. Next topic: Atlantic Meridional Overturning Circulation (AMOC).

Key People and Terms

Kuroshio Warm Pacific current off Japan
Humboldt Current Cold current of Peru and Chile
Gulf Stream Warm Atlantic current
Labrador Current Cold current off Canada
Benguela Current Cold current off southwest Africa
Equatorial Countercurrent Eastward warm flow near the equator

Exam Corner

Points to Remember

Kuroshio is to the Pacific what the Gulf Stream is to the Atlantic.
Peru and Benguela are cold currents.
Labrador meets the Gulf Stream at the Grand Banks.
The West Wind Drift circles Antarctica.
The countercurrent flows east.

Do Not Confuse With

Kuroshio and Oyashio Warm versus cold
Brazil and Falkland currents Warm versus cold
Canary and Guinea currents Cold versus warm

Memory Hook

West is warm, east is cold; where they meet, fog and fish.

Mains Angle

Questions link currents to climate. These points add depth.

Pattern Warm west, cold east
Effects Deserts, fog, fisheries
Change El Niño and AMOC

A Question You May Face

An original practice question, not a past paper question.

“Describe the major currents of the Pacific and Atlantic oceans and explain why cold currents are associated with deserts.”

How to Answer

Gyres Direction.
Pacific Warm and cold currents.
Atlantic Warm and cold currents.
Effects Deserts and fog.

GS Relevance

Prelims: names, location and nature of major currents, effects on climate and fishing. GS Paper 1: ocean currents and climate.

Frequently Asked Questions

What is the Kuroshio Current?

The Kuroshio is a warm, fast current of the western North Pacific, flowing northeast past Taiwan and Japan. It is the Pacific counterpart of the Gulf Stream, carries heat toward the mid-latitudes, and when it meets the cold Oyashio Current, it creates rich fishing grounds and fog.

What is the Humboldt or Peru Current?

The Humboldt or Peru Current is a cold current that flows north along the western coast of South America. It brings nutrient-rich water by upwelling, supports one of the world's richest fisheries, and helps to make the Atacama coast a desert. It weakens during El Niño.

Where does the Gulf Stream meet the Labrador Current?

The warm Gulf Stream meets the cold Labrador Current off Newfoundland on the Grand Banks. The meeting causes frequent fog and supports rich plankton and fish stocks. The Labrador Current also carries icebergs to this region, which is a hazard for shipping.

What is the Somali Current?

The Somali Current flows along the coast of East Africa. In the summer it flows northward as a fast current of more than 2 metres per second, with strong upwelling of cold, nutrient-rich water, and in winter it reverses and flows southward. It is the only western boundary current that reverses seasonally.

How do ocean currents affect climate?

Warm currents carry heat to higher latitudes and warm and moisten the air over coasts, as the Gulf Stream does for northwestern Europe. Cold currents cool the coasts, stabilise the air and cause dry or foggy conditions, as the Peru and Benguela currents do for the Atacama and the Namib.

PYQ Practice — Statement Analysis

1 The Benguela Current is a cold current off southwest Africa.

True

It is linked to the Namib Desert.

2 The Kuroshio is a cold current of the Pacific Ocean.

False

It is a warm current.

3 The Somali Current flows northward in summer.