Waves in the Ocean Wave Parameters Idealized Wave

Waves in the Ocean

Wave Parameters

Idealized Wave Spectrum

Properties of Ocean Waves ¥ An ocean wave is an undulation of the sea surface. – Wave crest – Wave trough – Wave height – Wave length – Wave period ¥ Progressive waves move across the sea surface. ¥ Standing waves oscillate about a fixed point.

What Causes Waves? ¥ Wind ¥ Submarine disturbance ¥ Gravitational attraction of sun and moon

Wind Generation of Waves ¥Wind velocity ¥Wind duration ¥Fetch (distance over which wind blows) ¥Simply put, wave size increases as all these factors increase.

Progressive Waves ¥ Wind-generated waves are progressive waves because they travel across the sea surface.

Progressive Wave Types ¥ Sea - irregular waves in the area of generation ¥ Swell - more regular waves beyond area of generation ¥ Surf - waves that have reached the coast, grow in height, and break

Wave Motions ¥ Forward movement of the wave form. ¥ Orbital motion of water particles beneath the wave. ¥ It is wave energy, NOT water molecules, that moves across the sea surface.

Flow of Energy, not Mass

Wave Motion with Depth

Deep Water Waves do NOT interact with the seafloor. Orbits of the water molecules are circular.

Shallow Water Waves DO interact with the seafloor. Orbits of the water molecules become elliptical.

Life History of Ocean Waves

Life History of Ocean Waves ¥ Waves originate in the fetch area. This area is characterized by a “confused” sea state with extensive wave interference. This interference may be – Constructive – Destructive

Rogue Waves? ¥ Constructive wave interference - wave buildup

Rogue Waves http: //bit. ly/9 XWFZu http: //bit. ly/cs 1 I 9 b http: //bit. ly/dm. Fs. I 7

Destructive Waves ¥ Destructive wave interference - wave cancellation

Progressive Wave Types ¥ Sea - irregular waves in the area of generation ¥ Swell - more regular waves beyond area of generation ¥ Surf - waves that have reached the coast, grow in height, and break

Transformation of Deep-water Waves: Dispersion

Shallow Waves Affected by Bottom ¥ In shallow water, the sea bottom transforms the wave’s properties. This leads to wave refraction and waves collapse forming surf (breakers).

Wave Refraction ¥ Bending of the wave crest as waves enter shallow water. It is due to – Drag along the bottom. – Differential speed along the crest.

Shallow-water Wave Transformations ¥ Interaction with the sea bottom. ¥ Bottom friction alters both the – Wave form ¥ Wavelength shortens (decreases) ¥ Height increases – Celerity (speed of wave form) ¥ decreases

Transformation of Shallow-water Waves

Progressive Wave Types Sea Surf Swell

Surf’s Up! Spilling Plunging, or Surging ¥ depending on the slope of the bottom

Back to Mavericks, CA Condition Black Video

Motion of Water Particles Beneath Waves