Vertical movements, often referred to as upwelling and downwelling, exhibit much lower speeds, amounting to only a few metres per month. As seawater is nearly incompressible, vertical movements are associated with regions of convergence and divergence in the horizontal flow patterns.
Upwelling
- Water that has greater density usually sinks to the bottom.
- However, in the right conditions, this process can be reversed.
- Denser water from the deep ocean can come up to the surface in an upwelling.
- Generally, an upwelling occurs along the coast when wind blows water strongly away from the shore.
- As the surface water is blown away from the shore, colder water from below comes up to take its place.
- This is an important process in places like California, South America, South Africa, and the Arabian Sea because the nutrients brought up from the deep ocean water support the growth of plankton which, in turn, supports other members in the ecosystem.
- Upwelling also takes place along the equator between the North and South Equatorial Currents.
