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”…

7. Moon’s gravitational attraction

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

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

11. 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…

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

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

14. Main Tidal constituents
Origin Symbol period coefficient generation
(hours)
Semidiurnal tides
Moon M semidiurnal principal lunar tide
Sun S semidiurnal principal solar tide
Moon N elliptical M2 tide
Diurnal tides
M&S K principal declination tide
Moon O diurnal principal lunar tide
Sun P diurnal principal solar tide

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

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

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

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

21. Co-tidal
Chart for
M2 tide

22. M2 tidal

24. Tidal Resonance: amplification of tidal signal (e. g
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.

25. Variations in tidal form world wide

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

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

28. Some engineering applications using tidal resonance and their effects

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

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

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

37. 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!

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

40. Tidal ellipses Residual (time-averaged) currents

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

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

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

47. Westward swimming
Northward swimming