Upwelling
As you have seen, 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 anupwelling(Figure14.19). 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.
Figure 14.19: An upwelling forces denser water from below to take the place of less dense
water at the surface that is pushed away by the wind. ( 9 )
Lesson Summary
- Ocean waves are energy traveling through the water.
- The highest portion of a wave is the crest and the lowest is the trough.
- The horizontal distance between two wave crests is the wave’s length.
- Most waves in the ocean are wind generated waves. Tsunami are exceptionally long
wavelength waves often caused by earthquakes. - Tides are produced by the gravitational pull of the Moon and Sun on Earth’s oceans.
- Spring tides happen at full and new moons, when the Earth, Moon, and Sun are all
aligned.