Waves and Tides
only generate currents, but also waves.
form as wind friction
stretches the surface. Wind deflected upward creates a partial
vacuum and atmospheric pressure push down on the wave from behind.
In deep water the circular motion of waves is virtually
friction-free. What does this
mean for the distance that swells can travel?
Continuation of wind energy can result in the formation of seas
Mature waves sort themselves into smooth undulations called swells
Is the forward
speed of a wave crest equal to the forward speed of the mass of water
contained in that wave (i.e. does wave speed = current speed)?
What is a 'wave' in physics?
Growth of wind generated waves is determined by:
- wind duration
- wind speed
Waves are sustained because
restoring forces (gravity in wind-generated waves) continue past the
water level of calm seas resulting
The speed of waves, wavelength, period and height are
inter-related (e.g. for
speed = gT/2Ï€).
Are longer wavelength waves faster?
waves maintain a circular path only when water depth from surface to
bottom is greater than one-half the wave length (deep-water waves
A wave at
any given location in the ocean is likely to be the result of
several independent wave trains arriving at that point at that
time. Interaction of wave trains can lead to destructive and
How can rogue waves be explained?
Other types of waves
Waves not generated by wind
include tides, internal
surges, seiches, and tsunamis
Theory of Tides
What is the main force generating tides?
How many high tides would
this generate per day?
Why along the Georgia coast are
two low and two high tides (diurnal), evenly space over
Why are high (and low) tide ~50 minutes
later every day?
What pattern in tidal range
becomes apparent when examining tidal ranges over 28 days?
Why does tidal range change at this
frequency and not just over 28 days? Hint: what other
astronomical body influences
gravitational and centrifugal forces?
the moon is smaller than the
sun, why does it have a greater effect on tidal bulging than the sun?
Does it matter in terms of tidal
strength whether the moon and sun are on opposite sides of the Earth or
on the same side?
So when is tide the highest, spring tide or
When is tide the lowest?
Dynamic Theory of Tides and other
Can you tell when it is high tide just by looking to see if the moon is
overhead? (Hint: recall from lab the times at which high tide
occurred along the East Coast; where they synchronous?).
Waves are not effected by friction with the ocean bottom when
ocean depth is deep relative to the wavelength. What is
the wave length of the tidal bulges created by the moon?
else effects with the tidal bulge as it travels around the Earth?
As the moon passes over a continent, what happens to the water that has
'piled' up on the eastern side of the contintent
The point of equilibrium (the node) of the slosh is
toward the center of the basin. Movement of the tidal crest
creates a sloshing in the basin, and the Coriolis effect spins the
water about the basin. This creates an amphidromic
point at its center, where
the tidal range is zero.
Does water slosh at the same rate in containers of different
In smaller basins, the natural sloshing of the basin can be the same as
the tidal cycle. What will
tidal range be like in this case? (i.e. what happens when the peaks of
two different wave trains coincide?) What will happen in a basin
the frequency of sloshing is twice that of the tidal frequency?
Interference also results as a result of coastal and bottom morphology.
In the funnel-shaped Bay of Fundy the
tidal range is a 2-meters at the
mouth of the bay and 11-meters at the head of the bay.
can form as crests move up rivers and estuaries.
Tidal prediction is further complicated
because the moon's orbit around the Earth is elliptical and the Earth's
axis of rotation is tilted with respect to the moon's orbit (and
similarly the Earth's orbit about the sun).
cannot be accounted for in
predictions made in tide tables?