Coastal Upwelling
Coastal upwelling is an oceanographic phenomenon in which wind-driven surface water is pushed away from the coast, causing cold, nutrient-rich water from deeper ocean layers to rise and replace it at the surface. This process is driven by the combined effects of prevailing winds blowing parallel to the coastline and the Coriolis effect, which deflects the surface water offshore — a process described by Ekman transport. Coastal upwelling regions are among the most biologically productive ocean areas on Earth, supporting major fisheries such as those off Peru, California, and West Africa.
Major Coastal Upwelling Zones and Their Ecological Significance
| Region | Driving Wind | SST Anomaly | Key Fish Species | Annual Fish Catch |
|---|---|---|---|---|
| Peruvian (Humboldt) | Southeast trades | −5 to −8°C | Anchoveta, sardine | ~10 million tonnes/yr |
| California Current | Northerly winds | −3 to −5°C | Salmon, sardine, anchovy | ~1 million tonnes/yr |
| Benguela (SW Africa) | Southeast trades | −4 to −6°C | Sardine, anchovy, hake | ~1.5 million tonnes/yr |
| Canary Current | Northerly winds | −3 to −4°C | Sardine, mackerel | ~2 million tonnes/yr |
| Somalia Current | SW monsoon winds | −3 to −5°C | Tuna, sardine | Moderate productivity |
Interactive Tools
NOAA CoastWatch Upwelling Index
Real-time coastal upwelling indices and sea surface temperature anomaly data
Open ToolNASA Earth Observatory: Upwelling
Satellite imagery and explanation of coastal upwelling and phytoplankton blooms
Open ToolKhan Academy: Upwelling
Lesson on Ekman transport, the Coriolis effect, and their role in driving coastal upwelling
Open Tool
Wikimedia Commons, CC BY-SA
Related Terms
Ocean Current
An ocean current is a continuous, directed movement of seawater generated by forces acting upon the water, including wind, the Coriolis effect, temperature and salinity differences, and tidal forces. Surface currents, driven primarily by wind, affect the upper 10% of the ocean, while deep-water currents are driven by density differences related to temperature and salinity. Ocean currents play a vital role in regulating global climate by redistributing heat from the tropics toward the poles and influencing weather patterns on nearby landmasses.
Thermocline
The thermocline is a distinct layer in the ocean — typically found between 200 and 1000 meters depth — where water temperature decreases rapidly with increasing depth, separating the warm, well-mixed surface layer from the cold, deep ocean. The main thermocline is a permanent feature of the tropical and mid-latitude oceans, with temperature dropping from about 20°C at the surface to 5°C at 1000 m depth, while seasonal thermoclines can form and dissipate in response to summer heating. The thermocline acts as a physical barrier that limits the exchange of nutrients, gases, and heat between the surface and deep ocean.
Marine Ecosystem
A marine ecosystem is a community of living organisms — including phytoplankton, zooplankton, fish, marine mammals, and benthic organisms — interacting with each other and their physical environment (water, light, temperature, salinity, nutrients) in the ocean. Marine ecosystems range from shallow coastal zones and estuaries to the open pelagic ocean, deep-sea hydrothermal vents, and polar seas, with each zone characterized by distinct biological communities adapted to its conditions. These ecosystems provide critical services including oxygen production (phytoplankton generate ~50% of Earth's oxygen), carbon sequestration, food security for billions of people, and climate regulation.
From Old English "up" and "wyllan" (to boil up, spring), combined to describe the upward movement of water. The scientific understanding of upwelling was developed in the early 20th century by Vagn Walfrid Ekman (1905), who described the wind-driven surface layer deflection now known as Ekman transport.