Oceanography Chapter 8- Waves

Waves

disturbances of energy in the ocean’s surface water (energy moves, not the waves itself)

What two wave types make orbital (cyclical) waves?

longitudinal and transverse

Longitudinal waves

wave particles move left and right parallel to energy transfer

Transverse waves

wave particles move up and down perpendicular to energy transfer

Crest

the highest point of a wave; the wave’s peak

Trough

the lowest point of a wave

Still water level

the theoretical level of water if no waves were present

Wavelength (L)

the distance between two waves (crest to crest or trough to trough)

Wave steepness

the ratio of a wave’s heigh to its length (H/L)

At what wave steepness does a wave break?

exceeding a ratio of 1/7

Wave period (T)

the TIME it takes for one full wave to pass a fixed point

Wave frequency (F)

the number of crests that pass a fixed point per unit of time (F=1/t)

What direction does the waveform transmit energy?

downward

Wave base

the depth at which wave energy is negligible, equal to half the wavelength (L/2)

Deep water wave

water is deeper than the wave base, doesn’t impact the seafloor

Deep water wave speed 

S=(L)/(T), S=1.25*sqrt(L), or S=1.56*(T)

Relationship between deep water wave length and speed

the longer the wavelength, the faster the wave speed

Shallow water wave

if water depth is less than 1/20 of the wavelength, touches the bottom so friction is a factor

Shallow water wave speed

S=3.13*(sqrt of depth)

Relationship between shallow water wave length and speed?

the deeper the water, the faster the wave

How do waves develop?

wind blows over the ocean’s surface and creates capillary waves (ripples), and as energy increases waves begin to develop as gravity waveshigher ener

Capillary waves

small, short-wavelength waves (ripples) on the ocean's surface caused by wind

Sea

the area where wind driven waves are generated

Fetch

distance over which wind is blowing in a constant direction, generating waves

What defines how big a wave gets?

wind speed, wind duration, and fetch

destructive wave interference

when two or more waves combine and cancel each other out, resulting in little to no amplitude

constructive wave interference

when two or more waves combine to create a wave(s) with larger amplitude

fully developed seas

a sea state where the waves have reached their max height for a given wind speed, duration, and fetch

swell

waves moving faster than the wind away from their originating sea, low steepness, symmetric waves, don’t lose energy over distance

spilling breakers

breaking waves that occur on gentle slopes, have low overall energy, and have turbulent mass

plunging breakers

breaking waves that occur on a moderately steep bottom and have higher energy than spilling breakers

surging breakers

breaking waves that occur on an abrupt slope and are highly energetic due to the compressed space

Converging orthogonals indicate what type of shoreline?

erosional shorelines, energy is concentrated

Diverging orthogonals indicate what type of shoreline?

depositional shorelines, energy is dissipated

wave train

a group of waves traveling in the same direction

wave reflection

the reflection of waves back into the ocean with little loss of energy

seiche

standing wave, the sum of two waves with the same wavelength moving in opposite directions, resulting in no net movement

tsunami

powerful shallow water ocean waves caused by sudden sea floor displacement, like seismic activity, moving water vertically dramatically

tsunami wavelengths

large wavelength, high speed, tall height

Why is tidal wave inappropriate to use?

tides are bulges caused by the gravitational pull of the Moon and Sun, not waves