Ocean Tides

1. Ocean Tides By Coach Murray

2. Lesson Objectives • Define the term tide • Explain examples of tidal range • Describe how an observer sees tides in real life • List reasons why tides are important • Explain the two major causes/types of tides • Describe how tides are predicted

3. Ocean Tides • What is a tide: • Is the periodic rise and fall of the sea surface • Noticeable against coastlines, not in the open ocean • Is just a long period wave

4. How do I observe tides? • 3 ways to observe tides: • High – maximum elevation of a tide • Low – fall in sea level to a minimum elevation • Slack – brief period of time in which water is neither rising or falling • Notation: • 0 is sea level, -0.5 is ½ ft. or 6” below sea level

5. What is tidal range? • Tidal range – vertical difference between high and low tides • Example • Nova Scotia • 0 to 35 ft range

6. Why are tides important? • General Navigation • Commercial harvesting • Hurricane damage prediction

7. Why are tides important?

8. Why are tides important?

9. The 2 major causes/types of tides Newton’s law says…gravitational attraction between the earth and • The moon (aka lunar tides) - Britanica video The major cause, closer to Earth 2) The sun (aka solar) The minor cause, further from Earth

10. How does the lunar tide work? Hypothetically, if earth was covered completely with water, two “bulges” of water would appear. • 1 bulge on side of earth facing the moon • 1 bulge on the opposite side of the globe As earth makes 1 complete rotation (in 24 hrs) a single point would experience 4 events • 1) high, low, high, low

11. How does the solar tide work? • Solar tide • IS NOT a separate set of tides • GIVES variation to the lunar tidal pattern • It is not referred to as the solar tide but the two effects is has on the lunar tide: • Spring tides Sun, moon, and earth are aligned (@ new and full moon – 2 x a month) Result: extra-high high tides and very-low low tides • Neap tides Sun and moon at right angles to each other (2 x a month) Result: partial cancelation of lunar tide = moderate tides

12. How does the solar tide work? • Solar tide • IS NOT a separate set of tides • GIVES variation to the lunar tidal pattern • It is not referred to as the solar tide but the two effects is has on the lunar tide: • Spring tides Sun, moon, and earth are aligned (@ new and full moon – 2 x a month) Result: extra-high high tides and very-low low tides • Neap tides Sun and moon at right angles to each other (2 x a month) Result: partial cancelation of lunar tide = moderate tides

13. How does the solar tide work? • The solar causes both spring and neap tides to happen to the lunar tide.

14. Realistic Tides are Patterned • Realistically our planet is not covered by water • Continental landmasses • Block westward passage of tidal bulges as earth rotates • Result: tidal patterns vary daily from ocean basin or in different regions of ocean basins • 2 highs, 2 lows (semidiurnal tide) • 1 high, 1 low (diurnal or daily tide) • 2 highs, 2 lows but successive high tides are quite different from each other (mixed semidiurnal)

15. Tide Predictions Tides for coastal ports and locations (Fort Morgan, Dauphin Island )are have been observed and recorded for years Future predictions of timing and amplitude are based on historical observations. Published years in advance in books, calendars, and online by location.

16. Tide Measuring Devices