The nature of the tidal force from the Moon and the Sun is well known, but the response of the Earth itself and the world oceans to this force is still a subject of research.
The tides in the Norwegian and Barents Seas display many fascinating complex dynamical features. Along the western coast of Norway and in the shallow parts of the Barents Sea the tidal currents are the dominant part of the current variability. The tidal current profoundly effects the mixing and renewal of water masses in the oceans. Thereby providing favorable conditions for many marine life forms. In this way the Moon has a fundamental effect on life on the planet Earth.
This lecture will review the status of our knowledge of tidal phenomena. Events with extreme high and damaging sea level are usually a joint effect of tides, storm surges, and high waves. In addition to possible sea level rise due to climate changes all this will effect construction and building activity in the coastal zone. The various complex mechanism influencing sea level changes on a long time scale will also be discussed.