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Abstract

The short-term variability of temperatures, residual currents, sea level, nutrients and salinity on time scales of days, weeks and months is mainly driven by weather events, while the basic features and the long-term variability of the North Sea as, for instance, mean salinity distribution, mean currents, yearly nutrient input by river discharge, distribution of fish species and their year-to-year variation, are mainly due to climate, i.e. the statistics of weather. Any change in climate which will mean systematically changed weather thus may have a strong impact on the North Sea as a whole. Since climate will change even without external forcing due to the interaction of climate system components on all time scales, the long-term basic features of the North Sea also have to change continuously. This Volume, therefore, is mainly a report of the contemporary North Sea characteristics, which are a mixture of natural and man-made contributions, both to mean values and variability. The separation of man's contribution is still not possible in many cases. This statement also holds for some of the trends observed during the last decades or the last century.