Types of Ocean Tides

If the ocean were a grand stage, tides would be its performers, moving gracefully under the influence of celestial forces. However, not all tides are the same—just like dancers follow different rhythms, tides vary in intensity and timing due to the changing positions of the Sun, Moon, and Earth. Let’s explore the different types of tides and what causes them.

The Basics: Why Tides Differ?

Although tides occur twice a day, they do not follow an exact 12-hour cycle. Instead, the interval between successive high tides is 12 hours and 25 minutes due to the Moon’s gradual movement in its orbit. Since the Sun and Moon exert different gravitational influences depending on their relative positions to Earth, tides display noticeable variations.

These variations give rise to several types of tides:

Spring Tide

Imagine a tug-of-war where both teams pull in the same direction. This is what happens during a Spring Tide when the Sun, Moon, and Earth align in a straight line (a position called Syzygy). The combined gravitational force of the Sun and Moon pulls ocean water more intensely, resulting in higher-than-normal high tides and lower-than-normal low tides.

Spring Tides occur:

• During the New Moon (when the Moon is between the Earth and Sun) → This position is called Conjunction.
• During the Full Moon (when the Earth is between the Sun and Moon) → This position is called Opposition.
• These tides rise about 20% higher than normal and occur twice every month.

Think of it as the ocean getting an extra push, swelling more than usual.

Neap Tides

Now imagine a tug-of-war where one team pulls sideways instead of forward. This is what happens during Neap Tides when the Sun, Earth, and Moon form a right angle (a position called Quadrature). Here, the Sun’s gravitational force counteracts the Moon’s pull, weakening the tide’s intensity.

• Neap Tides occur around the 7th and 8th day of each fortnight.
• High tides are about 20% lower than normal, while low tides are not as low as usual.

This is why some tidal cycles appear milder than others.

Tropical and Equatorial Tides – Unequal Tides

The Moon doesn’t always stay directly above the equator; it shifts north and south relative to Earth’s equator. This movement affects how tides behave at different latitudes.

• When the Moon is above the Tropic of Cancer, the tides are higher in the northern hemisphere than in the southern.
• When it is over the Tropic of Capricorn, the effect reverses.
• This phenomenon occurs twice every month and causes successive high and low tides of unequal height.

It’s like the ocean tipping slightly depending on the Moon’s location!

Perigean and Apogean Tides – The Moon’s Distance Matters

The Moon’s orbit around Earth isn’t a perfect circle; it’s slightly elliptical. This means the Moon sometimes comes closer to Earth (Perigee) and sometimes moves farther away (Apogee).

• When the Moon is closest to Earth (Perigee), its gravitational pull is strongest, creating Perigean Tides, which are higher than usual.
• When the Moon is farthest (Apogee), its pull weakens, leading to Apogean Tides, which are lower than usual.

If a Spring Tide coincides with a Perigean Tide, it results in exceptionally high water levels, sometimes causing flooding. Conversely, when Neap Tides align with Apogean Tides, tides are abnormally low.

Equinoctial Spring Tides

As Earth orbits the Sun, it experiences two equinoxes (March and September), when the Sun is directly over the equator. During this time:

• The gravitational forces of the Sun and Moon align strongly, producing higher-than-usual Spring Tides known as Equinoctial Spring Tides.
• These tides occur every six months.

Think of them as the Sun giving an extra pull to the tides, causing noticeable water level changes worldwide.

Rip Tides – The Misdirected Name

Unlike other tides, Rip Tides (also called Ebb Jets or Tidal Jets) are not caused by the Moon’s gravitational pull. Instead, they result from local shoreline features and sandbars that create powerful currents pulling water away from the shore.

• These currents move perpendicular to the coast, dragging swimmers out to sea.
• They can extend 200 to 2,500 feet in length but are usually less than 30 feet wide.

Despite their name, Rip Tides are not true tides. They are dangerous currents caused by coastal geography.

Conclusion

Tides are not just simple waves coming and going—they are complex, dynamic interactions between celestial bodies and oceanic forces. Whether it’s the Sun and Moon aligning for a mighty Spring Tide, the Moon’s distance altering tide strength, or local features creating deceptive Rip Tides, every tide tells a fascinating story of cosmic influence on Earth’s water.