1. Chapter 7 Waves in the Ocean Words from these PPT slides are already on the course web site.

2. Wave Parameters (Figure 7-1a)

3. Properties of Ocean Waves
An ocean wave is an undulation of the sea surface.
Wave crest
Wave trough
Wave height
Wave length
Wave period
Progressive waves move across the sea surface.
Standing waves oscillate about a fixed point.

4. What Causes Waves? Wind Submarine disturbance
Gravitational attraction of sun and moon

5. Wind Generation of Waves
The type of wave generated by wind is determined by:
Wind velocity
Wind duration
Fetch (distance over which wind blows)
Simply put, wave size increases as the strength and duration of the wind, and distance over which it blows increases.

6. Progressive Waves
Wind-generated waves are progressive waves because they travel across the sea surface.

7. Progressive Wave Types
Sea - irregular waves in the area of generation
Swell - more regular waves beyond area of generation
Surf - waves that have reached the coast, grow in height, and break

8. Wave Motions Two basic motions associated with an ocean wave
The forward movement of the wave form.
The orbital motion of water particles beneath the wave.
It is wave energy not water molecules that moves across the sea surface.

9. Flow of Energy,not Mass (Figure 7-2)

10. Wave Motion with Depth (Figure 7-3a)

11. Motion Animation

12. Deep Water Waves (Figure 7-4a)
Waves do NOT interact with the seafloor.
Orbits of the water molecules are circular.

13. Shallow Water Waves (Figure 7-4b)
Waves DO interact with the seafloor.
Orbits of the water molecules become elliptical.

14. Life History of Ocean Waves (Figure 7-7a)

15. Life History of Ocean Waves
Waves originate in the fetch area. This area is characterized by a “confused” sea state with extensive wave interference. This interference may be
Constructive
Destructive

16. Rogue Waves? (Figure 7-6b)
Constructive wave interference occurs when several wave crests or troughs coincide. The crests build up and the troughs build down.

17. Destructive Waves (Figure 7-6c)
Destructive wave interference occurs when the crest of one wave coincides with the trough of another wave resulting in a cancellation.

18. Progressive Wave Types
Sea - irregular waves in the area of generation
Swell - more regular waves beyond area of generation
Surf - waves that have reached the coast, grow in height, and break

19. Transformation of Deep-water Waves: Dispersion (Figure 7-7a)

20. Shallow Waves Affected by Bottom
In shallow water, the sea bottom transforms the wave’s properties. This leads to wave refraction and waves collapse forming surf (breakers).

21. Wave Refraction (Figure 7-8a)
Bending of the wave crest as waves enter shallow water. It is due to
Drag along the bottom.
Differential speed along the crest.

22. Shallow-water Wave Transformations
Interaction with the sea bottom.
Bottom friction alters both the
Wave form
Wavelength shortens (decreases)
Height increases
Celerity (speed of wave form)
decreases

23. Transformation of Shallow-water Waves (Figure 7-7b)

24. Progressive Wave Types
Sea
Swell
Surf
Surf

25. Surf’s Up! Spilling Plunging, or Surging
depending on the slope of the bottom
(Figure 7-9)

26. Condition Black Video

28. Motion of Water Particles Beneath Waves (Figure 7-3b)