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Lecture

Wave Height(Click for larger view). This global map shows wave height and direction for the major ocean basins. The colors indicate wave height – orange to red colors indicate higher waves. The white arrows indicate the direction the waves are traveling. Where are the highest waves found? Can you guess why? (Source: NOAA/NCEP Ocean Modeling Branch)

What is an ocean wave?

Simply defined, a wave is any disturbance created when energy moves through an object or substance. There are many types of waves caused by different forces – some examples are earthquakes, ocean waves, radio waves, visible light waves, and atmospheric waves. In all cases, waves carry energy through a medium (air, water, solid earth) but do not carry the medium itself. Think about “the wave” in a huge stadium – the people stand up and sit down, but they do not move from side to side. This gives the illusion of a large wave traveling around the stadium, but no people are moved!

In this module we will explore the formation and characteristics of ocean waves. Ocean waves are created by disturbances that transfer energy into ocean water. In this module, we will focus on wind waves to describe wave characteristics. However, it is important to keep in mind that the same processes act in all waves, regardless of the force causing them. At the end of this module, we will consider ocean waves caused by forces other than the wind like splash waves, internal waves, seiche and tsunami.

Wind Waves – An Introduction

The name “wind wave” is the name given to any wave that is created by the wind blowing over the ocean surface. In this case, the disturbing force is the energy transferred from the wind to the ocean surface. The ocean will carry this energy in the form of waves eventually releasing it along a shoreline. The size of wind wave will depend on three main factors: (1) the wind strength, (2) the wind duration, and (3) the uninterrupted distance over which the wind blows.

Look at the figure at the top of this page showing wave heights on July 17, 2007. Where are the highest (biggest) waves found? Most are found around Antarctica in the Southern Ocean. This is because this is one of the few places on Earth where very strong winds (the Easterlies and Westerlies) can blow for long distances and not be interrupted by landmasses. Large waves can also be produced during storm events like the typhoon that was just east of Japan on the day this image was created.

Wind waves are the most common type of wave in the ocean and are found superimposed on currents, tides, and tsunami. Wind waves are also common in other bodies of water like lakes, ponds and rivers. The larger the body of water, the bigger the wave we might expect to see. For example, Lake Superior of the Great Lakes of North America often has very large waves due to its orientation parallel to the prevailing winds.

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