‚€ 
Also in the case of the simulation of the pollution spreading over 
geveral years, the mean distribution corresponds to a distribution 
which was calculated with a wean circulation, 
The variability of the circulation, on the basis of the variabili- 
ty of the meteorological parameters, leads to large concentration 
variations of£ the pollutants, 
The monitoring of the North Sea should be fitted to the natural 
fluecetuations of the ecological system. 
Future Perspectives 
The simulations presented here serve two aims:! On the one hand, the 
estimate of the mean cireulation and its fluctuations; on the orther 
hand, the qualitative (relative) estimate of the transport routes of 
substaänces soluble in water. These results correspond to only a 
first step towards the actual final target dispersion models, namely 
the simulation of the natural transport routes of actual pollutants, 
In how far this final target can be fulfilled in the near future es- 
sentially depends upon the work of marine biologists and marine 
chemists. Only if it is possible to unequivocally describe the in- 
fluence of chemical and biological processes along the transport 
routes of substances can this be fitted into the model with the aid 
of mathematical equations or parameterizations. 
Quantitative estimate of concentration rates, with the aid of which 
the real pollutant burden of the North Sea will first be ascertain- 
able, are dependent upon the quality of the input data, 
Thereto belong especially the data concerning the types and quanti- 
ties of the river inputs (including their temporal. varilability) as 
well as wind and density data, For this marine scientists to carry 
out the measurements are particularly required. Not only the accu- 
racy of the measurement equipment, but also the temporal and spatial 
resolution of the measurements must be essentially Improved. 
Only under these pre-requisites is it possible for the "modelling” 
deeanographers to improve the dispersion models. 
For the monitoring of the North Sea, the dispersion models can al- 
ready provide a substantial contribution, On the basis of their spa- 
tially as well as temporally high resolution, they make possible a 
survey of the current pattern within the North Sea, 80 that by means 
öf the model results fitted measurement strategies can be developed.