Offshore wind farms are typically comprised of turbines, whose rotors convert mechanical energy from wind into electrical energy, and an offshore substation, which are linked to each other by a network of electrical cables. The electricity is transported onshore via export cables (which are typically buried in the seafloor) so that the energy can be integrated into the electrical grid. Turbines can either have fixed foundations, in which the foundation is driven into the seabed, or floating foundations, which have a series of anchors attached to the foundation via mooring lines. Floating turbine designs are newer and are generally deployed in much deeper waters (50-300 m, or 164-984 ft). For more detailed information and scientific citations, please see the full FAQ document linked below.

The primary factors associated with offshore wind development that may affect whales include underwater sound, vessel activities, and habitat change. Offshore wind development introduces a variety of sounds into the environment, particularly during wind farm construction, as well as additional boat traffic during construction, operations, and maintenance activities. In addition, offshore wind development could lead to changes in the habitats, which may result in either positive (e.g., artificial reef creation) or negative change (e.g., effective habitat loss). The potential impacts to individuals and populations from each of these changes will depend on multiple factors, including behavior, life history, population size, and habitat use. For more detailed information and scientific citations, please see the full FAQ document linked below.

There is no documented scientific evidence that offshore wind energy activities kill whales. While offshore wind energy development, like any marine development, has the potential to affect whales (see What are the potential effects of offshore wind development on whales?), the sounds produced during all phases (i.e., site assessment, construction, and operations) are insufficient to cause direct mortality. However, the sound emitted may impact hearing or behavior, and cumulation of sounds from anthropogenic sources may lead to chronic effects. There are various mitigation measures in place to reduce risk of potential impacts (see What mitigation measures are being required by regulators in the U.S. for offshore wind?) Collisions are a concern for all vessels in the marine environment across industries. Vessel collisions have the potential to injure or kill whales. However, offshore wind vessels comprise a very small portion of all vessels in the marine environment, and they operate in a more precautionary manner to avoid the types of collisions that occur with other industries, which reduces this risk (see What mitigation measures are being required by regulators in the U.S. for offshore wind?). For more detailed information and scientific citations, please see the full FAQ document linked below.

Sources of anthropogenic sound include vessels, offshore wind energy development, oil and gas exploration, military exercises, and other activities, all of which have the potential to affect marine mammals to varying degrees. Some anthropogenic sounds are high-intensity and acute (i.e., occur for short durations), while other types of sound are lower-level and chronic (i.e., occur consistently). Sound varies in intensity, frequency, and duration; all of these characteristics influence the potential for sound to affect marine mammals. For more information, see What are the effects of anthropogenic sound on marine mammals? Sounds produced in relation to offshore wind energy development vary by phase (e.g., site assessment, construction, operations, decommissioning). Some chronic sounds are lower intensity (“volume”) and are nearly continuous (e.g., operational turbine sound). Other offshore wind-related sounds are high-intensity and acute (e.g., pile driving of turbine foundations into the seabed). Offshore wind energy construction, marine oil and gas exploration, military sonar, and vessel activities all produce substantial amounts of underwater sound, but they differ in their intensity and frequency and therefore potential effects on marine mammals. For more detailed information and scientific citations, please see the full FAQ document linked below.

The contribution of offshore wind vessel activity to strike risk is generally considered to be very low both because of the small relative contribution of this industry to existing maritime vessel traffic, as well as the strict rules in place for offshore wind activities that are intended to reduce strike risk to whales. Offshore wind development involves many kinds of vessels over the life of a wind farm, and vessel needs change during each project phase. Vessel activity typically peaks during wind farm construction and immediately subsides post-construction to near pre-construction levels. Offshore wind vessel activity is subject to mitigation and monitoring measures that are not required of other maritime activity, including enhanced speed reduction, dedicated observers, and near-real time passive acoustic monitoring, all of which lower the strike risk profile for offshore wind vessels relative to vessels from other industries.

Like existing submarine power cables and to a lesser extent telecommunication cables, electrical cables that carry power from offshore wind developments to shore produce electric and magnetic fields (EMFs) that some marine species may be able to detect. Marine mammals likely use Earth’s magnetic field for migration, but they are not known to detect electric fields. There is currently no scientific evidence indicating EMFs from subsea cables of any kind affect marine mammals, but potential interactions and effects are not well studied. Key marine mammal prey species of forage fish, squid, and small crustaceans like copepods and krill are not known to be EMF-sensitive, so EMF effects on these organisms will likely be negligible.