Chapter 8: Waves and Water Dynamics

Wave Generation

• Wind: Primary disturbing force generating most ocean waves.
• Energy Transfer: 2% of atmospheric energy transferred to ocean surface by wind.
• Interfaces: Interaction of fluids with different densities (e.g., air-ocean, internal ocean waves).
• Internal Waves: Generated by density differences below surface, especially near the pycnocline.
• Wave Size: Can be very large, up to 100 meters.
• Hazards: Can be dangerous for submarines.

Wave Motion

• Energy Transfer: Waves are energy moving through the ocean (medium).
• Particle Motion: Up-and-down, back-and-forth, or circular/orbital paths.
• Energy Distribution: Varies based on wave type (wind-generated, tsunami, tidal).

Types of Waves

• Surface Waves: Generated at the air-ocean interface.
• Atmospheric Waves: Generated by large air masses with different densities.
• Internal Waves: Occur below the ocean surface between layers with different densities.

Wave Characteristics

• Height: Distance from crest to trough.
• Wavelength: Distance between successive crests.
• Wave Period: Time for one wavelength to pass a fixed point.
• Wave Frequency: Number of wave crests passing a point per unit time.
• Wave Base: Depth below which wave motion is negligible (1/2 wavelength).
• Wave Steepness: Ratio of wave height to wavelength, critical point at 1/7 for breaking waves.

Types of Waves (Cont.)

• Progressive Waves: Three types - longitudinal (compression/expansion), transverse (side-to-side), and orbital (circular).
• Longitudinal Waves: Compress and expand; travel through solids, liquids, and gases (e.g., sound waves).
• Transverse Waves: Side-to-side; travel only through solids (e.g., gym rope exercise).
• Orbital Waves: Circular motion of water particles in ocean waves.

Wave Behavior

• Deep Water Waves: Occur in water deeper than wave base, unaffected by sea floor.
• Shallow Water Waves: Occur in water shallower than 1/20 of wavelength, interact significantly with sea floor.
• Wave Speed (Celerity): Calculated as wavelength/period.
• Wind-Generated Waves: Begin as capillary waves, can grow into gravity waves with longer wind duration and higher speed.

Wave Refraction and Interference

• Wave Refraction: Bending of waves as they approach shore at an angle; uneven energy distribution along shorelines.
• Wave Interference: Interaction of wave systems causing constructive (in-phase) or destructive (out-of-phase) interference.
• Rogue Waves: Large, spontaneous waves caused by constructive interference.

Waves Near Shore

• Shoaling: Waves slow, increase in height, and steepen as they approach shore and interact with sea floor.
• Types of Breakers: Spilling (gently sloping), plunging (moderate slope, ideal for surfing), surging (steep slope).
• Surfing: Balancing buoyancy and gravity on a surfboard, speeds can reach 25 mph.

Tsunamis

• Causes: Earthquakes, underwater landslides, volcanic eruptions, meteorite impacts.
• Characteristics: Long wavelengths, behave as shallow water waves, high speeds (up to 300 mph).
• Historical Events: Sumatra (2004), Japan (2011); significant loss of life and property.
• Warning Systems: Pacific Tsunami Warning Center, DART buoys for detection and warning.

Renewable Energy from Waves

• Wave Energy: Potential source of renewable energy, though challenging due to environmental and technical issues.
• Projects: Various wave power projects globally, including the Limpet 500 in Scotland and a wave farm in Portugal.

Additional Concepts

• Wave Trains: Groups of waves with similar characteristics and speeds, leading wave dies out and new wave forms behind.
• Decay Distance: Distance over which waves transition from choppy to uniform swell.