- Key Concepts:
- A wave has both kinetic (moving) and potential (stored)
- Total wave energy of the oceans is the result of adding
together the energies of different types of waves.
- Once waves are created, they must have a restoring force
to sustain wave motion, but waves must be formed initially by a displacing
- Two restoring forces--gravity and surface tension--act
on all waves.
- Planetary waves (Kelvin, Rossby, Equatorial, and Yanai
waves) depend on the rotation of Earth for a restoring force.
- Surface waves are the waves that eventually break on
the beach. The restoring force is due to the large density contrast between
air and water at the sea surface.
- Internal waves are subsea waves and are similar to surface
waves in some respects. The restoring force is due to vertical density
gradients within the sea.
- Most waves are created by interactions of winds with
the water surface. Waves can also be created by:
- Impacts on ocean water (earthquakes, volcanic explosions,
seafloor slumps, etc.)
- Gravitational attraction between Earth, moon, and
- The passage of vessels or marine animals through the
- Impacts can create waves (with very long periods) called
tsunamis (seismic waves). Tsunami are occasional events and contribute
only a fraction of the total wave energy of the oceans, but they can be
- Winds never blow uniformly over the water because they
are highly variable both in time and space. This variablility is visibly
apparent to the ocean observer. Here are some descriptions:
- "Sea" - waves of different heights,
wave-lengths, and directions of travel
- Calm - waves are insignificant and the sea is flat
- Swell - waves are smooth, mostly of same wavelength
and from same direction.
- The maximum height of waves depends on wind speed and
the length of time the wind blows. It also depends on wind
is the distance over which it blows.
- The highest ocean waves are created when winds are strong
and blow persistently over long fetches.
- Steep-sided waves can be created when waves travel in
the direction opposite that of a strong ocean current. These waves create
hazards for shipping lanes.
- Three sources of heat have influence on the ocean:
- Solar energy
- Geologic sources:
- Heat generated by the radioactive decay of elements
- Heat left over from Earth's formation, and
- Human-induced through the burning of fossil fuels.
- Solar energy is by far the most important because it
is responsible for 3,200 times the contribution of the other two.