This literature review summarizes research on the environmental impacts of offshore wind farms, identifies gaps in current knowledge related to offshore wind energy, and makes recommendations for future research. The offshore wind energy industry in Europe is expected to grow rapidly: in the European Union, 69 wind farms in 11 countries have a combined capacity greater than 6.5 gigawatts (GW), and some projections predict a capacity of 40 GW by the year 2020. Despite expectations for the construction of large-scale offshore wind farms, little research has studied the effects of offshore wind farms on oceanography. Most research has focused on biotic effects including noise, bird collisions, mammalian avoidance, and the artificial reef effect. The following review will hypothesize the largest potential wind farm-induced impacts to oceanography and consequences that could result from changes to oceanography.
Oceanographic processes that could be affected by offshore wind farms are downstream turbulence, surface wave energy, local scour, inflowing currents, and surface upwelling. Existing research predicts that most wind farm-induced changes will be within the wind farm footprint or within natural variations. Some studies hypothesize that “extreme” scenarios could cause irreversible changes to shoreline deposition, upwelling patterns, or bottom oxygen levels, but this review found no research that quantified these changes with confidence. Potential connections exist between offshore wind farms, the alteration of oceanographic processes and changes to local sediment, nutrient, or phytoplankton regimes, but these connections have not been studied and are only speculative. Current numerical modeling research does little to predict the effects of large-scale construction, potential cumulative effects of multiple farms, or far-field effects at the coast.
This review therefore recommends that future numerical models focus on wind farms with hundreds of turbines, the interactions of multiple wind farms, and downstream changes due to wind farms. Observational studies are also necessary to validate the models, and extensive site-specific data collection is necessary to compare any changes to the natural ocean state. The conclusions and recommendations from this review will be used to inform research related to the Coastal Observation System for Northern and Arctic Seas (COSYNA) at the Helmholtz-Zentrum Geesthacht, which uses data from a marine observation network in the North Sea to validate and improve coastal modeling results. One core question that COSYNA seeks to address is how the offshore wind farms will locally and remotely affect the physical dynamics, sediment transport, and biological processes in the North Sea. The gaps in research and potentially relevant offshore wind farm impacts as identified by this review will guide future COSYNA projects including data collection, model development, and research cruise campaigns.