Coastal Circulation

This chapter indicates how tides, density gradients, and winds generate residual circulation in the coastal zone. The present focus is on tidally dominated regimes, in particular the northwest European Shelf Seas that surround the UK. Primary attention is on the relationship between the above forcing and the resultant dynamics (currents), the further issue of the interconnected impacts on turbulence, mixing, and stratification is described more fully in Chapters 2.02 and 2.05. In comparison with the primary forcing components, the energy content of these residual circulations may seem negligible. However, such circulations strongly influence the longer-term supply to and disposal from estuaries of salt, heat, sediments, nutrients, etc. While the associated horizontal distribution patterns clearly influence these exchanges, the vertical distributions of temperature and salinity generate significant density gradients that often result in opposing export and import of tracers between the surface and bed. In more exposed seas, such as the Brazilian Shelf, the Maine coast, and the California coast, direct oceanic influences may play a significant role. Likewise, along microtidal coasts wave influences, including setup, may be much greater (Chapter 2.10).