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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 variability
 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 essentially
 depends upon the work of marine biologists and marine
chemists. Only if it is possible to unequivocally describe the influence
 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 ascertainable,
 are dependent upon the quality of the input data,

Thereto belong especially the data concerning the types and quantities
 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 accuracy
 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 already
 provide a substantial contribution, On the basis of their spatially
 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.