Marine Upwelling Zones: Where the Ocean Feeds the World

Less than 1% of the ocean’s surface produces a fifth of the world’s fish catch. This article covers marine upwelling, the process behind that imbalance.

Where the Ocean Feeds the World

WorldGeo0016

THE MECHANISM

Ekman Transport

Wind pushes surface water aside, drawing deep water up

15-20% OF WORLD CATCH

Peru / Humboldt Current

Under 1% of ocean surface, one of the richest fisheries on Earth

LARGEST IN THE REGION

Somali Coast

Western Indian Ocean’s biggest upwelling system

FEB-SEPT

India’s West Coast

Seasonal upwelling from Karwar southward, monsoon-driven

The link: wind pattern determines fish catch, half a world away from where the wind blows.

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Must Know

• Marine upwelling brings cold, nutrient-rich water up from ocean depths to the surface. This fuels exceptionally high biological productivity.
• The main driving mechanism is Ekman transport. Coastal winds push surface water offshore, and deeper water rises to replace it.
• The Peru/Humboldt Current upwelling zone covers under 1% of the world’s ocean surface. It still supplies 15-20% of the global marine fish catch.
• The Somali coast hosts the largest upwelling system in the Western Indian Ocean, and ranks fifth globally by importance.
• India’s west coast, from Karwar southward, sees seasonal upwelling from February through August or September, tied to the southwest monsoon.

Good to Know

• India’s west coast upwelling is driven by the Findlater Jet, a strong low-level wind stream blowing during the summer monsoon at 10-12 metres per second.
• Wind-driven upwelling works through two related processes. Ekman transport moves water horizontally; Ekman pumping causes vertical suction from wind-stress patterns.
• Coastal upwelling zones make up a tiny share of total ocean area. Yet they form the foundation of some of the world’s most productive fisheries.

Test Yourself

Please wait…

1. What does marine upwelling bring from ocean depths to the surface?

Cold, nutrient-rich water

Warm surface currents only

Salt deposits

Volcanic sediment

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Great to Know

• Upwelling zones show how a purely physical process can shape an economy. Wind pattern and Earth’s rotation, not just fish stock or fishing effort, determine where an industry thrives.
• The Peru/Humboldt system’s productivity relative to its tiny area illustrates a broader oceanographic pattern. Nutrient supply, not surface area, is what drives fishery output.
• India’s monsoon-linked upwelling ties the country’s own weather system directly to its west-coast fishing economy. These are two systems that might otherwise seem unrelated.
• Upwelling depends on consistent wind patterns. Disruptions to those patterns, from climate shifts to El Niño events, can directly threaten fisheries far from where the wind itself changes.