Oceanography: Waves and Water Dynamics

A comprehensive set of 35 vocabulary flashcards covering the concepts, equations, classification schemes, coastal interactions, and historical events of ocean waves and water dynamics.

Disturbing force

The energy source that causes waves to form, such as wind blowing across the ocean surface, density differences between fluid interfaces, or seismic events.

Atmospheric waves

Waves that form at an air-air interface between air masses of differing densities.

Internal waves

Waves that propagate along the pycnocline at the water-water interface between water masses of different densities, often larger than surface waves and caused by tides, turbidity currents, winds, or ships.

Progressive waves

Waves that oscillate uniformly and travel forward through a medium without breaking.

Longitudinal waves

Waves in which particles vibrate back and forth parallel to the direction of wave energy propagation, such as sound or compression waves.

Transverse waves

Waves in which particles move back and forth perpendicular to the direction of wave travel, resembling the movement of a waving string.

Orbital waves

Waves in which particles move in circular or elliptical paths, characteristic of ocean surface waves that combine both longitudinal and transverse motions.

Wavelength ($L$)

The horizontal distance between corresponding points on two successive waves, such as from crest to crest or from trough to trough.

Wave height ($H$)

The vertical distance measured from the crest elevation down to the trough elevation of a wave.

Wave steepness

The ratio of wave height to wavelength ($\frac{H}{L}$); if this ratio exceeds $\frac{1}{7}$, the wave becomes unstable and breaks.

Wave period ($T$)

The time required for one full wavelength to pass a stationary reference point.

Wave frequency ($f$)

The number of wave crests that pass a fixed reference point each second, defined mathematically as the inverse of the wave period ($\frac{1}{T}$).

Wave base

The depth below calm water level equal to half the wavelength ($\frac{1}{2}\,L$), below which water motion due to surface waves is negligible.

Deep-water wave

A wave traveling in water where the depth ($d$) is greater than half the wavelength ($d > \frac{1}{2}\,L$), with speed depending solely on wavelength.

Transitional wave

A wave traveling in water depth between half and one-twentieth of its wavelength ($\frac{1}{20}\,L < d < \frac{1}{2}\,L$), where the wave begins to interact with the seafloor.

Shallow-water wave

A wave traveling in water where the depth ($d$) is less than one-twentieth of the wavelength ($d < \frac{1}{20}\,L$), with speed depending strictly on water depth.

Capillary waves

Small ripples with wavelengths less than $1.74\,\text{cm}$ generated by initial wind stress on the ocean surface, where surface tension serves as the restoring force.

Gravity waves

Waves with wavelengths greater than $1.74\,\text{cm}$ created as more wind energy enters the water, exhibiting pointed trochoidal crests and restored by gravity.

Fetch

The uninterrupted horizontal distance over open water across which wind blows in a constant direction to generate waves.

Whitecaps

Ocean breakers that form in open water when wind energy causes wave steepness to exceed the critical limit of $\frac{1}{7}$.

Swell

Uniform, symmetrical waves with long wavelengths that outrun shorter waves and travel away from their storm area of origin.

Wave train

A progression or group of waves traveling together that share similar wavelengths, periods, and speeds.

Constructive interference

A wave interference pattern created when in-phase wave trains with similar wavelengths overlap, combining crest-to-crest to produce waves of increased height.

Destructive interference

A wave interference pattern created when out-of-phase wave trains overlap such that crests align with troughs, cancelling wave energy and reducing wave height.

Mixed interference

A complex wave pattern produced when multiple swells with differing wavelengths and wave heights overlap, generating an irregular sea surface.

Surf zone

The nearshore coastal belt of breaking waves where shoaling causes deep-water waves to steepen and collapse.

Shoaling water

Water that gradually decreases in depth toward shore, causing wave velocity and wavelength to shorten while wave height increases.

Spilling breaker

A type of breaking wave formed on gently sloping bottoms where wave energy is gradually dissipated as turbulent foam continually spills down the front of the wave.

Plunging breaker

A type of breaking wave formed on steep beach slopes where the wave crest curls over an air pocket and plunges forward with high energy.

Surging breaker

A type of breaking wave formed on abrupt, steep bottom slopes where wave energy is compressed and surges directly onto the shoreline without spilling or curling.

Wave refraction

The bending of wave crests as they approach the shoreline at an angle, caused by the nearshore part of the wave slowing down in shallow water while the offshore part continues at higher speed.

Rip current

A narrow, fast-moving band of water flowing offshore, produced by a pressure gradient after breaking waves pile water onto the beach.

Tsunami

A series of seismic sea waves caused by sudden seafloor displacements that behave as shallow-water waves and can travel at speeds greater than $500\,\text{mph}$ in the open ocean.

2004 Indian Ocean Tsunami

A devastating tsunami on December 26, 2004, triggered by a magnitude $9.2$ earthquake displacing $1200\,\text{km}$ of seafloor off Sumatra, resulting in $230{,}000$ to $300{,}000$ fatalities across $11$ countries.

2011 Japan Tsunami

A destructive tsunami on March 11, 2011, caused by the magnitude $9.0$ Tohoku Earthquake in the Japan Trench, which generated a $15\,\text{m}$ ($49\,\text{ft}$) initial surge, killed $19{,}508$ people, and crippled the Fukushima Daiichi nuclear power plant.