What Causes Ocean Surface Waves?

According to George Karlenskit, author of "Introduction to Marine Biology" (2009), waves occur due to forces acting on the water's surface. The energy that brings the waves is either dissipated at sea or strikes a beach. The waves result from distant geological effects and may travel thousands of miles before striking land. For instance, the majority of the waves seen on ocean beaches result from distant winds and may range from small ripples to huge tsunamis.

Wind

Wind blowing in the ocean shoves the ocean water, transferring some of its energy into the water. The water then gains energy from the wind due to the friction between them. The resultant effect of the friction between the wind and the water surfaces is called wind-waves.

Tides

The cyclic rise and fall of large water bodies are called tides. They are caused by slight variations in gravitational interaction between the sun, moon and Earth. This causes the ocean to bulge towards the moon because of the increased gravitational attraction on the side of the Earth facing the moon. Another bulge is formed on the opposite side of the Earth facing away from the moon because the moon's gravity is very weak, making the moon the primary factor controlling the height and rhythm of tides. Since the Earth rotates while this process is happening, two tides occur each day.

Tsunamis

Tsunamis are also called seismic sea waves and are brought about by abrupt changes in the seafloor, mostly earthquakes. Other abrupt changes include volcanic eruptions, explosions, meteorites and landslides, but these are rare and not all earthquakes generate tsunamis and not all tsunamis caused by earthquakes can be felt by people. To cause a tsunami, the earthquake must be large, cause vertical movements at the sea floor and take place near or under the ocean. Oceans worldwide have been experiencing tsunamis, but the Pacific Ocean has been more vulnerable because the "Ring of Fire" along its ends. The United States Geological Survey defines the Ring of Fire as a zone of frequent earthquakes along the basin of the Pacific Ocean. The tsunami transmits large amounts of energy that is spread over the deep sea but on reaching shallow water the energy decreases in volume and can overwhelm anything along its path. A tsunami may last for several hours.

Storm Surge

Storm surges are associated with the weather and may be potentially dangerous, especially when they coincide with high tides. These surges are responsible for most of the flooding and destruction, as in the case of hurricanes. Severe hurricanes can produce a storm surge of up to 12 meters (40 feet) high. High air pressure pushes the sea level below while extremely low air pressure forms a mound of water that is carried along by the storm front. As the storm surge nears land, the mound of sea water transforms into a mass of wind-driven, elevated water causing large storm waves.

References

• "Introduction to Marine Biology"; George Karlenskit; 2009
• ScienceDaily: Ocean Surface Wave
• National Data Bouy Centre: NDBC Science Education Pages, What Causes Ocean Surface Waves?
• National Data Bouy Centre: What Causes Ocean Surface Waves?
• United States Search and Rescue Task Force: Tsunamis
• United States Geological Survey: Earthquake Glossary - Ring of Fire