1. Ocean waves

2. Wave characteristics
Average level
1 cycle
1 cycle
Cycle = one unit of a wave
1 cycle = one complete wave
Crest
Trough

3. Wave characteristics
Amplitude and Height
Amplitude
1 cycle
Height
Significant Wave Height (Hs) =
average height of the one-third highest waves
Height

4. Wave characteristics
Wavelength
wavelengthwavelength
amplitude

5. Wave characteristics
Frequency = how often the wave repeats itself (cycles) in one second.
Frequency = cycles per second = Hertz (Hz)
e.g., 4 Hz = 4 cycles /second
1st
1 sec.
4th

6. Wave characteristics
Period = the time it takes for a wave to complete one cycle.
period
.01
Time (sec.)
e.g., Period = 10 sec
Frequency = 1 = .10 Hz
10
Formula:
f = 1
p
p = 1
f
High frequency = small period
Low frequency = large period
10 20

7. Wave formation
Fetch = distance traveled by wind across open water.

8. Wave formation
Fetch = distance traveled by wind across open water.

9. Wave formation

10. Particle displacement –
Wave orbitals

11. Particle displacement –
Wave orbitals

12. Particle displacement –
Wave orbitals
Stokes Drift

13. Wave particle displacement -
Longitudinal

14. A wave moving onto the shore

15. A wave moving onto the shore

16. A wave moving onto the shore

17. A wave moving onto the shore

18. Longshore currents

19. Rip currents

21. Wave refraction
• Wave refraction
• Bending of a wave
• Causes waves to arrive nearly parallel to
the shore
• Consequences of wave refraction
– Wave energy is concentrated against the
sides and ends of headlands
– Wave energy is spread out in bays and wave
attack is weakened
– Over time, wave erosion straightens an
irregular shoreline

22. Wave refraction

23. Wave refraction

24. When do waves break?
– Limited by ratio between wave height and wave
length (H/L)
– Limiting steepness  1/7
How are they predicted?
– wave forecasting (or hindcasting) depends on
wind velocity, duration, and fetch (WaveWatch III)
– Linear wave theory predicts wave heights
Breaking Waves
http://polar.ncep.noaa.gov/waves/wavewatch/

25. Breaking Waves
• Spilling
• Plunging
• Surging

26. 11.19a-Segar, 2007

27. 10.18b-Garrison, 2005
Spilling breakers

28. 11.19b-Segar, 2007

29. 10.18a-Garrison, 2005
Plunging breakers

30. 11.19c-Segar, 2007

31. 11.19d-Segar, 2007

32. Wave erosion

33. Wave erosion
• Breaking waves exert a great
force
• Wave erosion is caused by
‒ Wave impact and pressure
‒ Abrasion by rock fragments

34. Wave erosion

35. Wave heights

36. Wave periods

37. Wave periods
• Larger wave period = higher energy = higher wave
• Wave height is limited by ratio between wave
height and wave length (H/L)
• Limiting steepness  1/7

38. Garret McNamara on 100 ft wave in Portugal 2014

39. Rogue Waves
Rogue waves can form from merging waves or
strong wind and waves plus opposing currents

40. 100 ft+ rogue wave in Southern Ocean
Rogue Waves

41. Rogue Waves