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Waves in the Ocean

Waves in the Ocean. Wave Parameters. Deep Water Waves. Waves do NOT interact with the seafloor. Orbits of the water molecules are circular . Wave Motion with Depth. Shallow Water Waves. Waves DO interact with the seafloor. Orbits of the water molecules become elliptical .

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Waves in the Ocean

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  1. Waves in the Ocean

  2. Wave Parameters

  3. Deep Water Waves Waves do NOT interact with the seafloor. Orbits of the water molecules are circular.

  4. Wave Motion with Depth

  5. Shallow Water Waves Waves DO interact with the seafloor. Orbits of the water molecules become elliptical.

  6. What Causes Waves? • Disturbing Force (pg. 231, Table 10.1) • Wind • Capillary wave • Wind wave • Submarine disturbance • Seiche • Seismic sea wave (tsunami) • Gravitational attraction of sun and moon • Tide

  7. Restoring Force • Dominant force that returns water surface to flatness • Capillary waves (surface tension) • Wind wave (gravity) • Seiche (gravity) • Seismic Sea Wave (gravity) • Tide (gravity)

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

  9. Deep-Water Waves • Wind-generated waves are progressive wavesbecause they travel across the sea surface. • Dispersion: waves separated by wavelengths and speed

  10. 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

  11. Swell Formation • Waves with longer wavelength move faster and leave the source area • Create regular, wind waves sorted by speed (dispersion) • Created by distant storms • Fast, medium, slow arrival

  12. Transformation of Deep-water Waves:Dispersion

  13. Wave Trains • Progressing group of swell with same origin and wavelength • Wave train moves forward only ½ the speed of individual waves • leading waves die out • Pg 235

  14. Factors Affecting Wave Development • Wind strength • Wind duration • Fetch: distance over which wind blows • Simply put, wave size increases as all these factors increase.

  15. Wave Height • Wind waves can exhibit a maximum 1:7 ratio of wave height to wavelength • This is called Wave Steepness

  16. Wave Interference • Constructive: additive formation of large crests • Rogue Waves

  17. Rogue Waves http://bit.ly/9XWFZu http://bit.ly/cs1I9b http://bit.ly/dmFsI7

  18. Wave Interference • Destructive

  19. Wave Velocity • Deep Water Waves • C = L/T • Celerity = Wavelength/Period • Celerity = speed of wave

  20. Example • What is the celerity of a wave with a wavelength of 335 meters and a period of 23 seconds? • 14.6 m/s

  21. 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).

  22. Waves Approaching Shore • “feels” bottom when depth is less than ½ wavelength • Front of wave slows, but back still moving at same speed • Forms sharp peak (approaches 1:7 ratio) • Wave breaks at 3:4 ratio (3 meter high wave will break in 4 meters of water)

  23. Wave Refraction • Bending of the wave crest as waves enter shallow water. It is due to • Drag along the bottom.

  24. Progressive Wave Types Swell Sea Surf

  25. Seiche • Rocking shallow-water wave • Usually in bays or harbors

  26. Tsunami • Extremely Long Wavelength (60-150 mi) • Up to 470 mph in open ocean

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