Ocean Wave
An ocean wave is a periodic disturbance at the sea surface in which energy is transferred through the water without the net transport of water itself — water particles move in circular or elliptical orbits as the wave passes. Most ocean waves are generated by wind transferring energy to the water surface through friction and pressure, with wave size depending on wind speed, duration, and fetch (the distance over which wind blows). Ocean waves are critical to coastal erosion, sediment transport, navigation safety, and marine ecosystems.
Key Formula
wave speed v = sqrt(g * lambda / (2 * pi)) for deep water waves
LaTeX: v = \sqrt{\frac{g\lambda}{2\pi}} \quad (\text{deep water})
| Symbol | Meaning | Unit |
|---|---|---|
| v | Wave speed (phase velocity) | m/s |
| g | Acceleration due to gravity (9.81) | m/s² |
| λ | Wavelength (crest-to-crest distance) | m |
| π | Mathematical constant (~3.14159) | dimensionless |
Worked Example
Problem
A deep-water ocean wave has a wavelength of 156 m. Calculate its wave speed and period. Use g = 9.81 m/s².
Solution
Step 1: Calculate wave speed using the deep-water dispersion relation: v = √(g × λ / (2π)) v = √(9.81 × 156 / (2 × 3.14159)) v = √(1530.36 / 6.2832) v = √(243.56) v = 15.61 m/s Step 2: Calculate period T = λ / v: T = 156 / 15.61 T = 10.0 s
Answer
Wave speed v ≈ 15.6 m/s; Wave period T ≈ 10 seconds.
Classification of Ocean Waves by Generating Force and Period
| Wave Type | Generating Force | Period | Wavelength | Example |
|---|---|---|---|---|
| Capillary waves | Surface tension | <0.1 s | <1.7 cm | Ripples on calm water |
| Wind waves | Wind stress | 1–30 s | 1–1000 m | Storm waves |
| Swell | Distant winds | 5–30 s | 100–1000 m | Open-ocean swells |
| Seiche | Atmospheric pressure | Minutes–hours | Basin scale | Bay oscillations |
| Tsunami | Earthquakes/landslides | 10 min–2 hr | 100–1000 km | 2004 Indian Ocean |
| Tidal waves | Gravitational forcing | ~12.4–24.8 hr | Half Earth circumference | Daily tides |
Interactive Tools
PhET Wave on a String
Interactive simulation demonstrating wave properties including amplitude, frequency, and wavelength
Open ToolNOAA Wavewatch III Forecast
Real-time global ocean wave forecasting model data and visualizations
Open ToolWolfram Alpha Wave Calculator
Calculate wave speed, period, and frequency from wavelength and depth
Open Tool
Wikimedia Commons, CC BY-SA
Related Terms
Tsunami
A tsunami is a series of long-wavelength, high-speed ocean waves generated by the sudden displacement of large volumes of water, most commonly caused by undersea earthquakes, volcanic eruptions, submarine landslides, or meteorite impacts. In the open ocean, tsunamis travel at speeds of 500–900 km/h with barely noticeable wave heights, but as they approach shallow coastal waters, they slow down and dramatically increase in height through shoaling, sometimes reaching heights of 30 meters or more. Tsunamis are among the most destructive natural hazards, responsible for widespread coastal flooding, loss of life, and infrastructure damage.
Tide
A tide is the periodic rise and fall of sea level caused by the gravitational forces exerted on Earth by the Moon and the Sun, combined with Earth's rotation. The Moon's gravity creates a tidal bulge on the side of Earth nearest to it and another on the far side, resulting in two high tides and two low tides in most locations every approximately 24 hours and 50 minutes. Tides are essential for coastal ecosystems, navigation, fishing, and are a significant source of renewable tidal energy.
Coastal Upwelling
Coastal upwelling is an oceanographic phenomenon in which wind-driven surface water is pushed away from the coast, causing cold, nutrient-rich water from deeper ocean layers to rise and replace it at the surface. This process is driven by the combined effects of prevailing winds blowing parallel to the coastline and the Coriolis effect, which deflects the surface water offshore — a process described by Ekman transport. Coastal upwelling regions are among the most biologically productive ocean areas on Earth, supporting major fisheries such as those off Peru, California, and West Africa.
Old English "wafian" (to wave, fluctuate) related to Old Norse "vafa" (to waver). The modern scientific study of ocean waves was formalized by George Biddell Airy (1801–1892) with Airy wave theory, and later extended by Stokes in the mid-19th century.