Coastal Environments and Global Change

4 Drivers: Waves and Tides

Daniel C. Conley

School of Marine Science and Engineering, University of Plymouth, Plymouth, UK

4.1 Physical drivers of the coastal environment

Waves and tides are the physical drivers that provide the energy for essentially all changes in coastal geomorphology. These drivers are derivatives of, respectively, solar energy and the gravitational pull of the Sun and the Moon. Significantly, it is gradients in these energy sources that lead to the creation of the forcing agents. Gradients in heating between different parts of the Earth cause the winds to blow across the surface of the ocean, which in turn generates the waves that efficiently transport this energy to distant locations. Gradients in the gravitational potential of the Moon and the Sun lead to the dramatic daily tidal variations in the level of the sea surface, which not only expose different sections of coastal geomorphology to wave attack but also generate strong tidal currents that also work to shape the morphology of the coast. Driven by gradients themselves, the waves and tides, which force coastal processes all over the globe, exhibit strong spatial and temporal variability that gives rise to the great variety present along the world’s coastlines. While ultimately driven by celestial forces that would appear to be beyond human influence, the details of where warming and cooling take place, as well the depths of the coastal basin where tides propagate, are affected by climate ...