Ocean Tides

MICRO-REALM 01

Tide Definition (NCERT)

PERIODICAL RISE & FALLOF SEA LEVEL

• The periodical rise and fall of the sea level, once or twice a day.
• Mainly due to the attraction of the sun and the moon.

MICRO-REALM 02

Tide vs. Surge (NCERT)

TIDE:
GRAVITY

SURGE:
METEOROLOGY

• Movement of water caused by meteorological effects (winds and atmospheric pressure changes) are called surges.
• Surges are not regular like tides.

MICRO-REALM 03

The Primary Driver (Moon)

← GRAVITY

• The moon's gravitational pull to a great extent is the major cause for the occurrence of tides.
• Because the Moon is much closer to Earth than the Sun.

MICRO-REALM 04

The Secondary Driver (Sun)

GRAVITY →

• To a lesser extent the sun's gravitational pull is a major cause for the occurrence of tides.

MICRO-REALM 05

Mass vs. Distance Rule

DISTANCE MATTERS MORETHAN MASS IN TIDAL FORCE

• Sun is 27 million times more massive than the Moon.
• But the Moon is ~390 times closer.
• Tidal force is inversely proportional to the CUBE of distance, making lunar pull 2.2x stronger.

MICRO-REALM 06

Centrifugal Force

←

→

• Centrifugal force is the other factor which acts to counterbalance gravity.
• Generated by the Earth-Moon system revolving around their common center of mass.

MICRO-REALM 07

The Twin Tidal Bulges

CENTRIFUGAL

• Together, the gravitational pull and the centrifugal force are responsible for creating the two major tidal bulges on the earth.
• One faces the moon (gravity), one faces away (centrifugal).

MICRO-REALM 08

High Tide (Crest)

HIGH WATER

• Occurs when a location rotates exactly under one of the two tidal bulges.
• Maximum water level (High Water).

MICRO-REALM 09

Low Tide (Trough)

LOW WATER

• Occurs when a location rotates into the "trough" exactly between the two bulges.
• Minimum water level (Low Water).

MICRO-REALM 10

Tidal Range

DIFFERENCE

• The difference between high water and low water.
• Varies greatly depending on coastal geometry and lunar phase.

MICRO-REALM 11

The Lunar Day Delay

24 HOURS + 50 MINSMOON ADVANCES IN ORBIT

• A tidal day is 24 hours and 50 minutes.
• Because while Earth rotates, the Moon also advances slightly in its orbit.
• Earth takes 50 extra minutes to "catch up" to face the Moon again.

MICRO-REALM 12

Semi-Diurnal Tide

HIGH

LOW

HIGH

LOW

• The most common tidal pattern.
• Featuring two high tides and two low tides each day.
• The successive high or low tides are approximately of the same height.

MICRO-REALM 13

Diurnal Tide

HIGH

↓ 12 HRS ↓

LOW

• There is only one high tide and one low tide during each day.
• The successive high and low tides are approximately of the same height.

MICRO-REALM 14

Mixed Tide

VARIATIONS IN HEIGHTWEST COAST OF N. AMERICA

• Tides having variations in height are known as mixed tides.
• These tides generally occur along the west coast of North America and on many islands of the Pacific Ocean.

MICRO-REALM 15

Syzygy (Straight Line)

• The position of both the sun and the moon in relation to the earth has direct bearing on tide height.
• When the sun, the moon and the earth are in a straight line.

MICRO-REALM 16

Spring Tide (Max Range)

MAXIMUM TIDAL RANGETWICE A MONTH (FULL/NEW MOON)

• When the sun, the moon and the earth are in a straight line, the height of the tide will be higher.
• These are called spring tides and they occur twice a month, one on full moon period and another during new moon period.

MICRO-REALM 17

Conjunction vs Opposition

CONJUNCTION (NEW MOON)

OPPOSITION (FULL MOON)

• Conjunction: Sun and Moon are on the SAME side of Earth (New Moon).
• Opposition: Sun and Moon are on OPPOSITE sides of Earth (Full Moon).
• Both produce Spring Tides.

MICRO-REALM 18

Quadrature (Right Angle)

• When the sun and moon are at right angles to each other.
• Occurs during the first quarter and third quarter moon phases.

MICRO-REALM 19

Neap Tide (Min Range)

MINIMUM TIDAL RANGEFORCES COUNTERACT EACH OTHER

• Normally, there is a seven day interval between the spring tides and neap tides.
• At this time the sun and moon are at right angles to each other and the forces of the sun and moon tend to counteract one another.

MICRO-REALM 20

Perigee (Moon Closest)

MOON AT CLOSEST POINTUNUSUALLY HIGH TIDES

• Once in a month, when the moon's orbit is closest to the earth (perigee), unusually high and low tides occur.
• During this time the tidal range is greater than normal.

MICRO-REALM 21

Apogee (Moon Farthest)

MOON AT FARTHEST POINTUNUSUALLY LOW TIDES

• Two weeks later, when the moon is farthest from earth (apogee), the moon's gravitational force is limited.
• The tidal ranges are less than their average heights.

MICRO-REALM 22

Perihelion (Jan 3)

EARTH CLOSEST TO SUNSLIGHTLY HIGHER RANGE

• When the earth is closest to the sun (perihelion), around 3rd January each year.
• Tidal ranges are also much greater, with unusually high and unusually low tides.
• (Conversely, Aphelion on July 4th produces slightly lower ranges).

MICRO-REALM 23

Flood Tide (Incoming)

→

• The time between the low tide and high tide, when the tide is rising, is called the flow or flood.
• Creates a strong landward current in coastal estuaries.

MICRO-REALM 24

Ebb Tide (Outgoing)

←

• The time between the high tide and low tide, when the water level is falling, is called the ebb.
• Creates a strong seaward current dragging sediment out to sea.

MICRO-REALM 25

Slack Water

STANDSTILL PERIODBETWEEN FLOOD & EBB

• The brief period at the exact peak of high tide or bottom of low tide.
• Tidal currents completely stop before reversing direction.

MICRO-REALM 26

Tidal Bore

→

• A steep, surging wave created when an incoming flood tide is funneled into a narrow, shallow river mouth.
• Famous in the Hooghly river (India) and Qiantang river (China).

MICRO-REALM 27

Bay of Fundy (Max Tides)

HIGHEST TIDES IN THE WORLD15 - 16 METERS (NOVA SCOTIA)

• The highest tides in the world occur in the Bay of Fundy in Nova Scotia, Canada.
• The tidal bulge is 15 - 16 m.
• Because there are two high tides and two low tides every day (roughly a 24 hour period); then a tide must come in within about a six hour period.

MICRO-REALM 28

Master Tide Matrix

GRAVITY vs CENTRIFUGALSPRING (SYZYGY)NEAP (QUADRATURE)FLOOD & EBB

• Completes the gravitational mechanics of the ocean.
• Locks the celestial alignments mapping.
• Transitions to Realm 92 (Ocean Currents).