Ocean TidesBy Coach Murray

Lesson ObjectivesDefine the term tideExplain examples of tidal rangeDescribe how an observer sees tides in real

lifeList reasons why tides are importantExplain the two major causes/types of tidesDescribe how tides are predicted

Ocean TidesWhat is a tide:

Is the periodic rise and fall of the sea surfaceNoticeable against coastlines, not in the open

oceanIs just a long period wave

How do I observe tides?3 ways to observe tides:1. High – maximum elevation of a tide2. Low – fall in sea level to a minimum

elevation3. Slack – brief period of time in which water is

neither rising or fallingNotation:

0 is sea level, -0.5 is ½ ft. or 6” below sea level

What is tidal range?Tidal range – vertical difference between

high and low tidesExample

Nova Scotia0 to 35 ft range

Why are tides important?General NavigationCommercial harvestingHurricane damage prediction

Why are tides important?

Why are tides important?

The 2 major causes/types of tidesNewton’s law says…gravitational attraction

between the earth and 1) The moon (aka lunar tides) - Britanica video

The major cause, closer to Earth

2) The sun (aka solar)The minor cause, further from Earth

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 moon1 bulge on the opposite side of the globe

As earth makes 1 complete rotation (in 24 hrs) a single point would experience 4 events1) high, low, high, low

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 tidesSun and moon at right angles to each other (2 x a month)Result: partial cancelation of lunar tide = moderate tides

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 tidesSun and moon at right angles to each other (2 x a month)Result: partial cancelation of lunar tide = moderate tides

How does the solar tide work? The solar causes both spring and neap tides

to happen to the lunar tide.

Realistic Tides are PatternedRealistically our planet is not covered by

waterContinental 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)

Tide PredictionsTides 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.

Tide Measuring Devices