1. Waves and Water Dynamics
Essentials of Oceanography

2. Pebble in Still Water
What happened when I dropped the pebble into the still tank?
Do the particles at the point of disturbance move outward too?
The surface of the water gets disturbed and it travels outward from the point of disturbance. This is a wave. Do the particles at the point of disturbance move outward too? Read more:

3. Cork in the disturbance
How does the cork move?
A disturbance travels from one point to another point away from the source, but there is no transport of material or medium itself.

4. What Causes Waves?
Waves are created by releases of energy (disturbances) including:
Wind
Movement of fluids of different densities
Mass movement into the ocean (splash waves)
Underwater sea floor movement (tsunami)
Pull of the moon and sun (tides)
Human activities

5. Most Ocean Waves Are Wind-generated

6. Anatomy of a Wave Crest- maximum elevation about still water level
Trough- max depression below still water level
Wavelength (L)- crest to crest, or trough to trough
Height (H)- vertical distance crest to trough
Amplitude- H/2, still water to crest or trough
Period (T) - time for one wavelength to pass a point
Frequency – number of wave crests passing a point in 1 second

7. Anatomy of a Wave

8. Wave Characteristics and Terminology (Continued)
If wave steepness exceeds 1/7, the wave breaks
Period (T) = the time it takes one full wave—one wavelength—to pass a fixed position

9. How do waves move?
1. The direction of propagation of wave, that is, the direction in which the disturbance travels.
2. The disturbance is transferred due to the oscillation of the particles of the medium involved. The direction of these oscillations is the second direction.
Longitudinal Waves : When these two directions are parallel.
Transverse Waves : When these two directions are perpendicular to each other.
Read more:

10. Types of Progressive Waves
Longitudinal
Back-and-forth motion
Transverse
Side-to-side motion
Orbital
Combination

11. Circular Orbital Motion
As a wave travels, the water passes the energy along by moving in a circular orbit
Floating objects also follow circular orbits

12. Orbital Motion in Waves
Orbital size decreases with depth to zero at wave base
Depth of wave base = ½ wavelength, measured from still water level

13. What about Surfing?
Here's what happens when the wave gets to water that's about half the depth of its wavelength:
The swells slow down as the water beneath them gets shallower. As a result, the waves get closer together, much the way a line of cars will get closer together if the car in front starts to slow down.
The leading edge of the swell becomes increasingly vertical as it slows while the trailing edge continues to look like a rounded slope.
The waves get taller as the solid surface under them and the waves' energy pushes the water upwards.
The exact shape of the ocean floor has a dramatic difference on how the waves break. If the shore slopes gently upward, the wave will gently spill over as it crests. A steep slope can cause waves that break suddenly and dramatically.
The cresting waves can travel for thousands of miles before reaching shore and becoming conducive to surfing.

14. Wave Characteristics Period (T) = time between wave crests
Is a constant for any wave
Function of the disturbing force
If wind energy decreases
Speed and wavelength can decrease
Period does not change
Wavelength 
Size of the orbits
Water depth relative to wavelength 
Shape of the orbits

15. Deep- and Shallow-water Waves
Deep-water waves
Water depth > wave base
Shallow-water waves
Water depth < 1/20 of wavelength

16. Deep Water Waves Orbits don’t reach the seafloor
Water depth > ½ wavelength
If L = 20 m, depth > 10 m
Only wind waves can be deep water waves
Wavelengths for tsunamis and tides are so long (100’s – 1000’s km)
Seafloor maximum depth = 11 km
Ocean depth would need to be >50 km for these to be deep water waves
Body surfing St Aug. 2 m  wavelength > 40m
Earth’s circ = ~40,000 km tide wavelength = 20,000
Water depth would have to be 10,000 km

17. Shallow Water Waves Orbits reach and interact with the seafloor
Water depth < 1/20 wavelength
Orbits “feel” the bottom
Orbits flatten  elliptical
Water at seafloor moves back and forth
1/20 wl > water depth >1/2wl

18. Wave Speed (S) General formula: Deep-water waves:
Wave speed (S) in meters per second = 1.56 T in seconds
Wave speed (S) in feet per second = 5.12 T in seconds
Shallow-water waves: (d = water depth)

19. Producing Waves Disturbing Force = energy input
Wind = wind waves*
Landslide/faulting = tsunami
Moon/sun gravitation = tides
Restoring Force = returns water to flatness
Tends to overcompensate leading to oscillations
Surface tension- for small waves (capillary waves)
Gravity for larger waves- nearly friction-free travel long distances

20. History of a Wave Wind waves = wind energy transferred to the water
Wind blows on the water – friction causes stretching of the surface
Ripples (capillary waves) form
Wind’s energy transferred to the water to drive the wave forward
Larger surface area more energy transferred = bigger waves

21. Factors Controlling Wave Height
Wind strength
Strong wind = more energy = taller waves
Wind duration
How long the wind blows in one direction
Waves produced by strong winds will dissipate when wind stops
Fetch - distance wind blows in one direction
Longer continuous input = taller waves

22. Fully Developed Sea Factors that increase wave height:
Increasing wind speed
Increasing duration (time) of wind
Increasing fetch (distance)
A fully developed sea is the maximum height of waves produced by conditions of wind speed, duration, and fetch

23. Largest Wind-generated Waves Authentically Recorded
In 1935, the vessel USS Ramapo experienced large waves while crossing the Pacific Ocean
Wave height was measured at 34 meters (112 feet)

24. Waves at the Shore

25. Waves Undergo Physical Changes in the Surf Zone

26. Surf Zone As waves approach the shoreline: Become shallow water waves
Slow down due to friction
Become closer together
Steepen
Break
Lose energy