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

1. Chapter 7Waves in the OceanWords 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 wavesmove across the sea surface. • Standing wavesoscillate about a fixed point.

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

5. Wind Generation of Waves • Wind velocity • Wind duration • Fetch (distance over which wind blows) • Simply put, wave size increases as all these factors increase.

6. Progressive Waves • Wind-generated waves are progressive wavesbecause 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 • Forward movement of the wave form. • 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 - wave buildup

17. Destructive Waves(Figure 7-6c) • Destructive wave interference - wave 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 refractionand 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 Swell Sea Surf

25. Surf’s Up! SpillingPlunging, orSurging • depending on the slope of the bottom (Figure 7-9)

26. Condition Black Video

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