How do ocean waves work

Understand ocean waves on coasts better

Most of the waves are caused by wind blowing over the ocean surface. Exceptions are, for example, the tidal waves triggered by the tide and tsunamis caused by seaquakes.

When the wind becomes extremely strong, the waves cannot grow indefinitely. Once a certain wave steepness has been reached, the wave breaks. It gives off energy and becomes smaller. Neither the relationships between the growth of the waves nor the release of wave energy when the waves break have been scientifically well understood.

In order to decipher these processes, the sea surface and the near-surface part of the water column are observed with measurements on site, so-called “in-situ measurement methods”, as well as with remote sensing methods. In the Radar Hydrography Department at the Helmholtz-Zentrum Geesthacht, innovative measurement techniques based on radar (Fig. 2) are developed and used to measure oceanographic parameters such as waves, currents and winds as well as the morphology of the seabed and the water depth (bathymetry) in the coastal area examine.

In order to precisely record the interactions between currents, the water depth and the ocean waves, special radar devices and modern video technologies are being developed. The new radar methods have a decisive advantage: They provide a three-dimensional image of the waves and their movement. Figure 2 shows the use of this method on the North Sea island of Sylt.

Radars are cheap in many ways. While with the traditional in-situ measurement methods, such as swell measuring buoys or wave levels, individual waves quickly pass the respective position, the waves can now be tracked in space and time. Radar devices also offer a decisive advantage: They provide continuous data day and night, while video cameras can only be used in daylight.