Waves Transmit energy (not mass) across the ocean’s surface Wave – disturbances caused by the movement of energy through some medium (solid, liquid, gas)

Waves Most generated in the open ocean Wave height depends on Wind velocity Wind duration FETCH – distance over which the wind blows – usually generated by a big storm

Waves Described by Crest – highest part Trough – lowest part Wavelength (L) – distance between crests/troughs Wave Height (H) – vertical distance between crest and trough Wave Period (T) – time for successive waves to pass a fixed point

Waves Wave Period (T) – time for successive waves to pass a fixed point Frequency – number of wave crests/troughs passing a fixed point every second

Types of Waves Deep Water Waves Move through water > ½ wavelength of the wave Do not feel the bottom Wave motion is circular

Types of Waves Shallow Water Waves Move through water < ½ wavelength of the wave Feel the bottom Cannot move in a circular path, only back and forth Most waves are shallow water waves

Deep Water Waves Move in an orbital / circular motion Waves do not carry water very far, but transfer energy Diameter of circle decreases with depth Wave motion non-existent below ½ wavelength

Deep Water Waves When waves approach shore Interact with seabed when depth equals ½ the distance between wave crests Orbits become restricted and elliptical Waves slow down and bunch up Waves become shallow water waves Eventually they form breakers

Breakers At water depths < ½ wavelength, waves feel the bottom Wave height increases Wave length decreases Velocity decreases because waves are dragging on the bottom Wave period stays the same When wave reaches 1.3 H => Breakers

Wave Refraction Wave crests can refract, or bend, if they approach the shore at an angle Caused by the change in velocity of waves as a function of water depth Only a small part of each wave feels bottom at a time so only a small part of wave slows

Waves Classified By- Disturbing force – energy that causes the wave to form Restoring force – force that returns the water surface to flatness after the wave formed Wavelength – longest waves move the fastest

Types of Waves Capillary waves – first to form when wind blows Important in transferring energy from air to water to drive ocean currents Wind waves – form when wind blows over ocean surface Both are deep water waves

Types of Waves Seiche – pendulum-like rocking of water in a basin No crest or trough

Types of Waves Tsunami – caused by the rapid displacement of ocean water When caused by the sudden vertical movement of Earth along faults called seismic sea wave Also caused by landslides, icebergs calving, volcanic eruptions, asteroid impacts

Types of Waves Tsunami Resemble fast, onrushing tide Not dangerous in open water Can travel at 212 meters per second (470 mph)

Shallow Water Waves Seiches, tsunami and tides are all shallow water waves They have extremely long wavelengths They are always in water less than ½ their wavelength The waves move extremely fast Tides move at a rate of 1600km (1000 mi) per hour

Rogue Waves Rogue waves are caused when wave trains traveling at different speeds and directions meet. They appear suddenly and may capsize boats.