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Tides Tide producing forces Semi-diurnal; diurnal tides Lunar and solar tides Resonance Shallow water waves Tidal ellips

Tides Tide producing forces Semi-diurnal; diurnal tides Lunar and solar tides Resonance Shallow water waves Tidal ellipses Tidal residuals Tidal-stream selective transport. England. San Francisco. Philippines. Korea. Not this kind of “tidal wave”…. Moon’s gravitational attraction.

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Tides Tide producing forces Semi-diurnal; diurnal tides Lunar and solar tides Resonance Shallow water waves Tidal ellips

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  1. Tides Tide producing forces Semi-diurnal; diurnal tides Lunar and solar tides Resonance Shallow water waves Tidal ellipses Tidal residuals Tidal-stream selective transport

  2. England San Francisco Philippines Korea

  3. Not this kind of “tidal wave”…

  4. Moon’s gravitational attraction

  5. The point “Z” stays fixed, and the earth-moon system rotates about it

  6. Force imbalance in earth-moon system creates tidal bulges

  7. By the time the Earth has completed one revolution (one day), the moon has moved slightly, so the Earth needs to rotate a bit more to catch up with the moon…

  8. M2 period (12.42 hours) Semi-diurnal period

  9. Declination offsets bulge from the equator (Diurnal period)

  10. Main Tidal constituents Origin Symbol period coefficient generation (hours) Semidiurnal tides Moon M2 12.42 0.91 semidiurnal principal lunar tide Sun S2 12.0 0.42 semidiurnal principal solar tide Moon N2 12.66 0.17 elliptical M2 tide Diurnal tides M&S K1 23.94 0.53 principal declination tide Moon O1 25.82 0.38 diurnal principal lunar tide Sun P1 24.07 0.18 diurnal principal solar tide

  11. Sun and moon effects can be additive or not…

  12. Amphidromic point (point around which tides propagate and where tidal elevation at a minimum)

  13. Kelvin wave:propagates with the coast on its right in the northern hemisphere and its amplitude decays offshore

  14. M2 cotidal charts for the Atlantic Ocean Amplitude (cm) Phase(degrees)

  15. Co-tidal Chart for M2 tide

  16. M2 tidal

  17. Tidal Resonance:amplification of tidal signal (e.g., amplitude) that occurs in an embayment or on a shelf, when the “length” of the embayment or shelf is near one-quarter of the wavelength of the wave.

  18. Variations in tidal form world wide

  19. semidiurnal Mixed, SD dominant Mixed, D dominant diurnal

  20. Bay of Fundy – tide gets huge (15 m) because of resonance High tide Low tide (6 hours later)

  21. Some engineering applications using tidal resonance and their effects

  22. Tidal currents (tidal ellipses) 60m 100m 200m

  23. Shallow water waves:Wavelength long relative to water depth Deep water waves:Wavelength short relative to water depth

  24. Velocity felt all the way to the bottom Velocity decays before reaching the bottom

  25. Tidal currents – can be very complicated (from near Australia) Current hodograph shows direction and speed of slow every hour (each point) over 15 days. Pattern doesn’t even repeat!

  26. Biological applications… Tidal residuals Transport Retention Selective tidal-stream transport

  27. Tidal ellipsesResidual (time-averaged) currents

  28. Another way of looking at residual currents... this time in the English Channel and North Sea

  29. Plaice migration: as adults they migrate from the feeding areas to the spawning grounds and back. How do they do it?

  30. Simulated tracks with day-night (diel) vertical migration: not much net displacement

  31. Westward swimming Northward swimming

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