Upwelling is the rise of cold, nutrient-rich deep water toward the ocean surface. It fuels plankton blooms,
supports major fisheries, cools coastlines and can trigger dramatic marine ecosystem changes.
What Is Upwelling?
Upwelling happens when deep ocean water rises toward the surface. This water is usually
colder and richer in nutrients than surface water. Once it reaches sunlit waters, those nutrients can
feed phytoplankton, the tiny marine plants at the base of the ocean food web.
How Upwelling Works
Upwelling often begins when winds push surface water away from a coastline or away from the equator.
Deeper water then rises to replace it. Earth’s rotation helps steer this movement through the
Coriolis effect.
- Wind pushes surface water away.
- Cold deep water rises to replace it.
- Nutrients reach the sunlit surface ocean.
- Phytoplankton blooms feed fish, seabirds and marine mammals.
Why Upwelling Matters
- Supports some of the world’s richest fisheries.
- Feeds plankton blooms and marine food webs.
- Cools coastal waters and nearby air.
- Can influence fog, coastal weather and ocean temperatures.
- Brings deep-water chemistry to the surface, including low-oxygen or acidic water in some regions.
Major Upwelling Regions
| Region | Why It Matters |
|---|---|
| California Current | Supports fisheries, kelp forests and productive coastal ecosystems. |
| Peru-Humboldt Current | One of the most productive fishing regions on Earth. |
| Benguela Current | Fuels rich marine life off southwest Africa. |
| Canary Current | Supports productivity off northwest Africa. |
| Equatorial Pacific | Strongly linked to El Niño and La Niña climate patterns. |
Coastal Upwelling vs. Equatorial Upwelling
Coastal upwelling occurs when winds drive surface water away from land, allowing deep
water to rise near the coast. Equatorial upwelling occurs where trade winds push surface
water away from the equator, pulling colder water upward from below.
Upwelling and El Niño
In the tropical Pacific, normal upwelling brings cold nutrient-rich water to the surface. During
El Niño, this upwelling can weaken, warming
surface waters and disrupting fisheries, rainfall patterns and marine ecosystems.
Can Upwelling Be Dangerous?
Upwelling is usually beneficial, but it can also bring low-oxygen, acidic or nutrient-loaded deep water
to the surface. In some cases, this contributes to fish kills, harmful algal blooms or marine dead zones.
The ocean gives with one hand and occasionally slaps with the other.
Related Ocean Topics
Frequently Asked Questions
What is upwelling?
Upwelling is the rise of cold, nutrient-rich deep ocean water toward the surface.
What causes upwelling?
Upwelling is mainly caused by winds pushing surface water away from a coastline or the equator,
allowing deeper water to rise and replace it.
Why is upwelling important?
Upwelling supplies nutrients to the sunlit surface ocean, supporting plankton blooms, fisheries,
seabirds and marine mammals.
Where does upwelling happen?
Major upwelling zones occur along the west coasts of continents, including California, Peru,
northwest Africa and southwest Africa, and along the equatorial Pacific.
How does El Niño affect upwelling?
El Niño can weaken normal upwelling in the tropical Pacific, warming surface waters and disrupting
fisheries and weather patterns.
