Humboldt Current

Also called: Peru Current, Peruvian Current · Topic: Movements of Ocean Water: Waves, Tides and Currents · NCERT: Class 11, Ch 4 "Climate"; Class 11, Ch 9 "Atmospheric Circulation and Weather Systems"; Class 11, Ch 13 "Movements of Ocean Water"

Meaning

The Humboldt Current (also called the Peru Current) is a cold ocean current that flows north along the west coast of South America, past Chile and Peru. Near the equator it turns west and joins the South Equatorial Current.

It matters because it causes strong upwelling (cold, nutrient-rich water rising from the deep). This upwelling supports the world's largest single-species fishery. The current also helps create the Atacama, the driest non-polar desert on Earth. When El Niño comes, warm water replaces the cold current, and these effects break down.

Explanation

Place in the South Pacific gyre

• Gyre means a large loop of ocean currents that turns around an ocean basin. NOAA calls it "a large system of swirling ocean currents" [3].
• Why the South Pacific gyre turns anticlockwise:
• The trade winds push water west near the equator. The westerlies push it east in mid-latitudes.
• The Coriolis force (the turning effect of the Earth's spin) bends moving water to the left in the Southern Hemisphere.

• So the South Pacific gyre turns anticlockwise.

• The Humboldt Current is the gyre's eastern side. It flows north, from cold, high latitudes towards the equator.

• It is an eastern boundary current, which means a current on the eastern edge of an ocean basin. Such currents are usually cold and bring upwelling [2].

How upwelling works here (cause → process → result)

• Cause: offshore winds
• Winds blow from the land out to sea. These winds are called offshore winds.

• The south-east trade winds drive them, helped by the South Pacific high-pressure cell.

• Process: deep water rises

• The winds push warm surface water away from the coast.

• Cold, deep water rises to take its place. It is rich in oxygen and nutrients [2].

• Result: a food chain

• The nutrients feed plankton (tiny floating plants and animals).
• The plankton feeds huge numbers of fish, mainly the Peruvian anchoveta.
• Seabirds eat the anchoveta. Their droppings pile up on coastal islands as guano, a natural fertiliser.

How it shapes the climate: the Atacama Desert

• Cold water cools the air above it from below.
• Cool air near the surface with warmer air above is stable. Stable air does not rise.

• Air that does not rise cannot form rain clouds.

• Result: the Atacama in northern Chile is the driest non-polar desert on Earth.

• The same pattern explains other west-coast deserts between about 20° and 30° latitude.

When the current fails: El Niño

• El Niño is a warm phase of the Pacific. Warm water spreads east and replaces the cold Humboldt water off Peru and Ecuador.
• The name: "El Niño" is Spanish for "the child", meaning the Christ child. Fishermen named a warm, southward-flowing current after it because it came off Peru and Ecuador every year around Christmas [4].
• The chain of events:
• The trade winds weaken, and the South Pacific high weakens.
• Upwelling falls. Warm water with few nutrients covers the coast.
• Plankton dies off, fish move away or die, and guano birds starve.

• Peru's normally dry coast gets heavy rain and floods.

• How the fish respond: during El Niño, the fish first move closer to the coast, then into deeper water, and finally south [2].

Where it occurs

• Course: it runs along the west coast of South America, past Chile and Peru. Near the equator it turns west and joins the South Equatorial Current.
• Upwelling coast: Peru and northern Chile. This is the coast to mark on a map.
• Atacama Desert: northern Chile, on the land next to the cold current.
• Guano islands: coastal islands off Peru, where seabird droppings collect.
• El Niño zone: the coasts of Peru and Ecuador, where warm water replaces the Humboldt water.
• Link to India: the current does not reach India. But El Niño, which pushes the Humboldt water aside, is linked to a weaker Indian monsoon. This link is called a teleconnection, meaning that weather in one part of the world affects weather far away.

Don't confuse with

• El Niño current: this is warm and flows south off Peru and Ecuador around Christmas. The Humboldt Current is cold and flows north.
• East Australian Current: this is on the western side of the same South Pacific gyre. It is warm, flows south and bathes the Great Barrier Reef. The Humboldt is the cold current on the gyre's eastern side.
• California Current: this is the Northern Hemisphere twin of the Humboldt. Both are cold eastern boundary currents with upwelling and dry coasts. But the California Current flows south, because the North Pacific gyre turns clockwise.
• Kuroshio–Oyashio meeting zone: this rich fishing ground off Hokkaido forms where a warm and a cold current mix. The Humboldt fishery comes from upwelling along one cold current.

Prelims Hooks

• The Humboldt (Peru) Current is cold and flows north, not south. Questions that say it flows south are a common trap.
• Humboldt Current → upwelling → Peruvian anchoveta, the world's largest single-species fishery [2].
• Humboldt Current → stable, dry air → Atacama (northern Chile), the driest non-polar desert.
• "El Niño" means "the Christ child". Peruvian fishermen named it after warm water that came around Christmas [4].
• The anchoveta fishery collapsed after the 1972–73 El Niño [4].
• The Humboldt Current is part of the anticlockwise South Pacific gyre. Its warm partner on the western side is the East Australian Current.

Mains Points

• Cold currents, upwelling and fishing economies (GS-I/III):
• Upwelling along the Humboldt coast makes Peru a top fishing nation. Guano from seabirds adds farm wealth.
• El Niño breaks this chain. The 1972–73 El Niño led to one of the most serious collapses in fisheries history [2].
• Over the last seven decades, El Niño years cut catches of the worst-hit species in the South-east Pacific by about 0.28 million tonnes a year on average, mostly anchoveta [2].

• In 2022–23, the South Pacific high weakened and upwelling fell. A coastal El Niño in 2023 badly hit anchoveta catches [2]. This shows that economies built on fishing face climate risk.

• Currents shape coastal climate (GS-I): a cold current cools the air from below. Stable air brings fog and dry coasts. The Atacama is the best example, so use it when explaining why west-coast deserts form between about 20° and 30° latitude.

• El Niño as a disaster and teleconnection issue (GS-III):
• When El Niño replaces the Humboldt water, Peru gets floods and a fishery collapse [4].
• India gets a weaker monsoon.
• This makes the case for ocean monitoring and ENSO forecasting, such as the work of INCOIS (Indian National Centre for Ocean Information Services).

Related concepts

• Kuroshio Current
• North Pacific Drift
• California Current
• Oyashio Current
• East Australian Current

Read more

• Currents of the Pacific Ocean