Ocean Waves: from surf to wave physics

So far this week you’ve studied currents – water moving from place to place. Waves are different: when a wave rolls past, the water mostly stays put, and it is energy that travels. In this lecture, Serena Illig starts at the shore, with waves we all recognise, and builds up the physics of how they really work.

The lecture moves through:

• What a wave is – an oscillation around equilibrium, restored by gravity, that carries energy across the sea while the water moves back and forth in place
• Describing a wave – amplitude, wavelength, period, and the idea of phase speed (how fast a crest travels)
• Wave groups and dispersion – why the ocean surface is a mix of many waves, why long waves outrun short ones, and how energy travels at the “group speed”
• How wind builds waves – the way wind blowing over the sea amplifies ripples into waves, and how stronger, longer-lasting winds build bigger seas
• Motion beneath a wave – the circular orbits water follows, and how they fade with depth
• Deep water and shallow water – why the same wave behaves differently depending on how its wavelength compares to the depth
• At the coast – how waves slow, steepen, grow, break in the surf zone, and bend (refract) to line up with the shore

The lecture closes by connecting all this to forecasting: how operational wave models represent the sea not wave by wave, but as a statistical spectrum of energy. As always, focus on the physical pictures rather than the mathematics.