10.7: How Waves Form

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Miracosta Oceanography 101
Miracosta)

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How Waves Form

When the wind starts to blow, the surface of a water body will go through a progression as waves form and intensify. When the wind starts to blow, the ocean surface will change from calm (mirror-like) conditions to form capillary waves (ripples), chop, wavelets, to waves (each with increasing wavelengths, wave heights, and wave periods). Smaller wave features can form on existing larger wave features, adding to the complexity of the water's surface.

Ripples (Capillary Waves)

Capillary waves are very small waves with wavelengths less than 1.7 cm or 0.68 inches (Figure 10.18). The formation of capillary waves is influenced by both the effects of surface tension and gravity. The ruffling of the water’s surface due to pressure variations of the wind on the water. This creates stress on the water and results in tiny short wavelength waves called ripples. Ripples are often called capillary waves. The motion of a ripple is governed by surface tension. They are the first waves to form when the wind blows over the surface of the water and are created by the friction of wind and the surface tension of the water. These tiny little waves increase the surface area of the sea surface and if the wind continues to blow, the size of the wave will increase in size and become a wind wave.

Figure 10.18. Capillary wave (ripples) forming next to a calm area (Lake Hodges, CA)

Chop

Chop refers to small waves causing the ocean surface to be rough. Ripples and small wavelets form and move independently of large waves moving through an area, creating rough and irregular wave patterns (Figure 10.19).

Figure 10.19. With increasing fetch, ripples merge to become wavelets in choppy surface water conditions.