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

Chapter 7 Waves in the Ocean Words from these PPT slides are already on the course web site. Wave Parameters (Figure 7-1a). Properties of Ocean Waves. An ocean wave is an undulation of the sea surface. Wave crest Wave trough Wave height Wave length Wave period

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

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  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 • 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 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 • 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 of Water Particles Beneath Waves(Figure 7-3b)

  12. Motion Animation

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

  14. Shallow Water Waves(Figure 7-4b) Waves interact with the seafloor are known as Orbits of the water molecules become elliptical.

  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 interferenceoccurs when several wave crests or troughs coincide. The crests build up and the troughs build down.

  17. Destructive Waves(Figure 7-6c) • Destructive wave interferenceoccurs 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 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) • decreases

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

  24. Surf’s Up! • Shore breakers (surf)are collapsing waves. Breaking is determined by wave steepness • Wave height/wave length. • When this value is about 1/7, waves begin to break.

  25. Waves Breakby SpillingPlunging, orSurging • depending on the slope of the bottom (Figure 7-9)

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