Waves in the OceanWaves in the Ocean

Words from these PPT slides are Words from these PPT slides are already on the course web site.already on the course web site.

Wave ParametersWave Parameters

Properties of Ocean WavesProperties of Ocean Waves An ocean wave is an undulation of the sea An ocean wave is an undulation of the sea

surface.surface.– Wave crestWave crest– Wave troughWave trough– Wave heightWave height– Wave lengthWave length– Wave periodWave period

Progressive wavesProgressive waves move across the sea surface.move across the sea surface. Standing wavesStanding waves oscillate about a fixed point.oscillate about a fixed point.

What Causes Waves?What Causes Waves?

WindWindSubmarine disturbanceSubmarine disturbanceGravitational attraction of sun and Gravitational attraction of sun and

moonmoon

Wind Generation of WavesWind Generation of WavesWind velocityWind velocityWind durationWind durationFetch (distance over which wind blows)Fetch (distance over which wind blows)Simply put, wave size Simply put, wave size increasesincreases as all as all

these factors these factors increaseincrease..

Progressive WavesProgressive Waves Wind-generated waves are Wind-generated waves are progressive progressive

waveswaves because they travel across the sea because they travel across the sea surface. surface.

Progressive Wave TypesProgressive Wave Types

SeaSea - irregular waves in the area of - irregular waves in the area of generationgeneration

SwellSwell - more regular waves beyond area - more regular waves beyond area of generationof generation

Surf Surf - waves that have reached the coast, - waves that have reached the coast, grow in height, and breakgrow in height, and break

Wave MotionsWave Motions ForwardForward movement of the wave form. movement of the wave form. OrbitalOrbital motion of water particles motion of water particles beneathbeneath

the wave.the wave. It is It is wave energywave energy,, NOT water molecules, NOT water molecules,

that moves across the sea surface.that moves across the sea surface.

Flow of Energy, not Mass Flow of Energy, not Mass

Wave Motion with DepthWave Motion with Depth

Motion AnimationMotion Animation

Deep Water WavesDeep Water Waves

Waves do NOT interact with the seafloor. Waves do NOT interact with the seafloor.

Orbits of the water molecules are Orbits of the water molecules are circularcircular..

Shallow Water WavesShallow Water Waves

Waves DO interact with the seafloor.Waves DO interact with the seafloor.

Orbits of the water molecules become Orbits of the water molecules become ellipticalelliptical..

Life History of Ocean WavesLife History of Ocean Waves

Life History of Ocean WavesLife History of Ocean WavesWaves originate in the fetch area. Waves originate in the fetch area.

This area is characterized by a This area is characterized by a “confused” sea state with extensive “confused” sea state with extensive wave interference.wave interference. This interference This interference may be may be –ConstructiveConstructive

–DestructiveDestructive

Rogue Waves?Rogue Waves?

Constructive wave Constructive wave interference - interference - wave wave buildupbuildup

Rogue WavesRogue Waves

http://bit.ly/cs1I9b http://bit.ly/9XWFZu http://bit.ly/dmFsI7

Destructive WavesDestructive Waves

Destructive wave Destructive wave interference - interference - wave wave cancellationcancellation

Progressive Wave TypesProgressive Wave Types

SeaSea - irregular waves in the area of - irregular waves in the area of generationgeneration

SwellSwell - more regular waves beyond area - more regular waves beyond area of generationof generation

Surf Surf - waves that have reached the coast, - waves that have reached the coast, grow in height, and breakgrow in height, and break

Transformation of Deep-water Waves:Transformation of Deep-water Waves:DispersionDispersion

Shallow Waves Affected by Shallow Waves Affected by BottomBottom

In shallow water, the sea bottom In shallow water, the sea bottom transforms the wave’s properties. transforms the wave’s properties. This leads to This leads to wave refractionwave refraction and and waves collapse forming waves collapse forming surfsurf (breakers).(breakers).

Bending of the Bending of the wave crest as wave crest as waves enter waves enter shallow water. It shallow water. It is due tois due to– Drag along the Drag along the

bottom.bottom.

– Differential Differential speed along the speed along the crest.crest.

Wave RefractionWave Refraction

Refraction AnimationRefraction Animation

Shallow-water Wave Shallow-water Wave TransformationsTransformations

Interaction with the sea bottom. Interaction with the sea bottom. Bottom friction alters both theBottom friction alters both the–Wave form Wave form

Wavelength shortens (decreases)Wavelength shortens (decreases) Height increasesHeight increases

–Celerity (speed of wave form)Celerity (speed of wave form) decreasesdecreases

Transformation of Shallow-water WavesTransformation of Shallow-water Waves

Progressive Wave TypesProgressive Wave Types

SeaSea SwellSwell

SurfSurf

Surf’s Up! Surf’s Up! SpillingSpillingPlunging, orPlunging, orSurgingSurging

depending on the depending on the slope of the bottomslope of the bottom

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Condition Black VideoCondition Black Video

Motion of Water Particles Beneath Motion of Water Particles Beneath WavesWaves