Summary, Conclusion, and Outlook - On the Effect of Offshore Wind Farms on the Atmosphere and Ocean Dynamics - page 144

lasted over 2 days after turning off the wind turbines, but due to the appearance of
inertial oscillation in model runs, the OWF effect on the ocean system can vanish
faster.
Evaluation with model results, taken around the test wind farm alpha ventus,
shows a good agreement of the OWF effect on the ocean

s temperature stratifica-
tion. The model restrictions only lead to expected discrepancies in the horizontal,
but the main simulated phenomena of up- and downwelling cells causing changes in
the temperature stratification are also established in nature.
Simulations over the German Bight underline that detected influences of OWFs,
presented under theoretical assumptions, show that the impact can be intensified in
reality. Addicted to meteorological situation and conditions of boundary layer,
OWFs mostly have a cooling effect under realistic conditions. Instead of the
vertical cells, belts of vertical motion, with maxima of

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10 m/d, occur depending
on wind direction, which controls the establishment of the surface elevation dipole
structure. The OWF induced atmospheric cooling, respectively warming, is
stamped on SST, which is also changed by an identified switch of the SST front
due to the wake in the ocean

s horizontal velocity field. Theoretically, SST can vary
due to the operating wind turbines by

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1 C.
Finally, such imposed dynamical and hydrographic modifications on the ocean
system by OWFs yield to questions about possible variations on the ocean ecosys-
tem and especially about biological consequences.
The theoretical approach of the dynamical analysis, influenced by OWF results,
can be transferred to each offshore wind farm location in the world. Technically, it
is possible to build OWFs along all coasts around the world. Independent of the
habitat, physical up- and downwelling will occur. And there are plans all over the
world to use offshore wind energy. So assuming that installed offshore wind farms
will consistently operate, the described influence of OWF on the atmosphere and,
especially, on the ocean will be of permanent duration in the future. The meteoro-
logical warming and cooling, as well as cloud dissipation and fog production, can
affect local climates over time.
Regarding the ocean ' s effect, the surface elevation can impact shipping and
storm surges, but the important OWF effect on the ocean is the occurrence of
vertical motion, and so the influence on the ocean s stratification will be dominant.

A warming or cooling of the upper layers and mixing over the whole water depth
will have consequences on the ecosystem. The response of the ecosystem to the
vertical mixing regarding nutrients, plankton, and other microorganism depends on
the habitat. But the OWF induced upwelling, in comparison with the coastal up- and
downwelling, is special because water that carries the properties of the ecosystem
will have relevant consequences on the mixed layer, as mentioned already by
Brostr¨m.
Additionally, an impact on mammals is possible. For example, the simulated up-
and downwelling belts in the North Sea can trigger distribution of common
porpoise (personal correspondence with Michael D¨hne).

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