Waves, Tides and Currents

Waves

What Are Waves?

Waves are movements on the ocean’s surface caused by energy passing through the water, resulting in a circular motion of water particles. They transmit energy, not water mass, across the ocean’s surface.

How Are Waves Formed?

Waves are classified based on their energy source:

• Surface Waves: Caused by wind blowing along the air-water interface, creating disturbances that grow as the wind continues to blow.
• Tsunamis: Created by submarine earthquakes or landslides that displace a large amount of water quickly, leading to long waves.
• Storm Surges: Caused by severe storms with high winds and low-pressure systems, leading to a significant rise in sea levels upon reaching the shore.

Factors Determining Wave Intensity

1. Wind Strength: Wind must move faster than the wave crest to transfer energy effectively.
2. Wind Duration: Longer winds generate larger waves.
3. Fetch: The uninterrupted distance over which wind blows without changing direction.

Classifying Waves

Waves are classified based on:

• Disturbing Force: The energy source that creates the wave.
• Free vs. Forced Waves: Whether they continue after the energy source stops.
• Restoring Force: What brings the wave back to equilibrium.
• Wavelength: Distance between wave crests.

Relation of Waves and Currents

• Upwelling: Occurs when winds push surface water away, causing colder, nutrient-rich water to rise, leading to high biological productivity.
• Rip Currents: Localized currents flowing away from the shoreline, typically through low spots or breaks in sandbars.
• Longshore Currents: Run parallel to the shore, moving sediment and causing erosion.

Advantages of Wave Energy

• Renewable, predictable, and accessible.
• Can harness energy without damaging land.

Disadvantages of Wave Energy

• Limited to coastal areas.
• Can disturb marine habitats and create noise pollution.

Tides

What Are Tides?

Tides are the regular rise and fall of sea levels caused by the gravitational pull of the moon and the rotational force of the Earth. Most shorelines experience two high and two low tides within a 24-hour period.

Types of Tides

• High Tide: Water reaches its highest point on the shore.
• Low Tide: Water recedes to its lowest point.
• King Tide: Exceptionally high tide occurring when the moon is closest to the Earth.
• Spring Tide: Highest tide, occurring when the sun and moon align.
• Neap Tide: Lowest tide, occurring when the sun and moon are at right angles to each other.

How Do Tides Work?

• The moon’s gravitational pull creates bulges in the ocean on the side facing the moon and the opposite side.
• The Earth’s rotational force and the sun’s gravitational pull also affect tides.
• The rise and fall of tides create intertidal zones that support unique marine ecosystems.

Effects of Tides

• Influence marine ecosystems, particularly the intertidal zone.
• Affect coastal areas, marine organisms, and human activities.

Theories of Tides’ Origin

1. Equilibrium Theory: Newton’s theory assumes an ideal, uniform ocean covering the Earth. It explains the basic formation of tides but is limited in explaining their actual occurrence.
2. Progressive Wave Theory: Suggests that tidal waves move from east to west, modified by the Earth’s landmasses.
3. Dynamic Theory of Tides: Laplace’s theory accounts for the Earth’s rotation, ocean basin depth, and width, and explains the behavior of tides more accurately.
4. Stationary Wave Theory: Proposes that tides are due to stationary waves that originate in each ocean independently.

Water Currents Generated by Tides

• Flood Currents: Move seawater toward the coast.
• Ebb Currents: Move seawater away from the coast.
• Rotary Currents: Circular movements in open seas, rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
• Reversing Currents: Form in shallow, near-shore areas with fast movement.

Ocean Currents

What Are Ocean Currents?

Ocean currents are the general movement of large masses of water in a specific direction. They are generated primarily by planetary winds and friction between the atmosphere and the ocean surface.

Types of Ocean Currents

1. Surface Ocean Currents: Extend up to 500-1000m in depth.
2. Deep Ocean Currents: Reach depths of up to 1.5 km.

Consequences of Ocean Currents

1. They follow global wind patterns.
2. Their speed depends on wind speed.

Factors Modifying Ocean Currents

1. Coriolis Force: Deflects currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
2. Coastline Orientation: Affects the direction and flow of currents.

Salinity Gradients

Vertical ocean currents, known as thermohaline currents, are driven by differences in water density caused by variations in temperature and salinity. These currents move slowly but can turn the ocean water over decades.

Mechanism of Ocean Currents

• Ocean water consists of multiple layers influenced by planetary winds, and these layers are deflected at an angle.
• Western Intensification: The phenomenon where western boundary currents are faster, deeper, and narrower than their eastern counterparts.

Conclusion

Waves, tides, and ocean currents are essential components of the ocean’s dynamic system. They play crucial roles in regulating marine ecosystems, influencing coastal environments, and impacting human activities. Understanding these oceanic movements is vital for navigation, climate prediction, and harnessing renewable energy.

1. How do upwelling and downwelling processes impact marine ecosystems and the productivity of coastal regions? (250 words)
2. Explain the role of the moon’s gravitational pull and the Earth’s rotation in the formation of tides. How do these factors contribute to the occurrence of spring and neap tides? (250 words)
3. Discuss how the Coriolis force and wind patterns influence the formation and direction of surface ocean currents in different hemispheres. (250 words)