Offshore wind farms reshape the North Sea
https://www.hereon.de/innovation_transfer/communication_media/news/104924/index.php.en
Downwind of the wind turbines, the so-called atmospheric wakes develop. These are characterised by reduced windspeed as well as specific pressure conditions and enhanced air turbulence. During stable atmospheric circumstances, the wind speed deficits spread up to 70 km behind the wind farms.
Using high-resolution hydrodynamic computer simulations, the team analysed the effects on the southern North Sea for the summer of 2013 (May to September)…The wake effects are sufficiently potent to redirect the existing currents. This results in shifting mean temperatures and a changed salinity distribution in the wind farm areas. “While the occurring changes remain within the range of interannual variability, they illustrate similar magnitudes as the presumed mean changes due to climate change or year-to-year variability,” says Nils Christiansen, from the Hereon Institute for Coastal Systems, who was lead author on the study.
Another wake effect is the reduction of shear-driven processes at the sea surface. In other words, the turbulent mixing of the water surface caused by shear wind is reduced dozens of kilometres around the wind farm…
"The magnitude of the induced mean changes does not indicate severe local effects, however far-reaching structural changes in the system occur“, says Christiansen.
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