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Earth and Space Sciences · Glossary

What is Upwelling?

Definition 6.7 High School Earth and Space Sciences · Chapter 6 — The Layered Ocean

Upwelling is the rise of cold water from below the surface layer, to replace surface water that the wind pushes away. It occurs along some coasts and in the open ocean.

Coastal upwelling off Peru (schematic cross-section from west to east, not to scale): the wind blows along the shore towards the equator, northward, into the page; the surface water is turned to its left and pushed out to sea; cold water from below the thermocline rises near the coast to replace it.
Coastal upwelling off Peru (schematic cross-section from west to east, not to scale): the wind blows along the shore towards the equator, northward, into the page; the surface water is turned to its left and pushed out to sea; cold water from below the thermocline rises near the coast to replace it.
The chlorophyll of the phytoplankton seen from space, averaged over 2002–2010: from dark blue (very little) through light blue to yellow (a lot); land in grey. The coast of Peru and the band along the equator in the Pacific stand out; the gyres are deep blue. Image: Jesse Allen and Robert Simmon, NASA Earth Observatory (public domain).
The chlorophyll of the phytoplankton seen from space, averaged over 2002–2010: from dark blue (very little) through light blue to yellow (a lot); land in grey. The coast of Peru and the band along the equator in the Pacific stand out; the gyres are deep blue. Image: Jesse Allen and Robert Simmon, NASA Earth Observatory (public domain).
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