Floating offshore wind farms are progressing into deeper ocean areas. Operators will need to detach entire multi-megawatt turbines and tow them back to land for more intensive repairs. Researchers recently finished the first-ever acoustic audit for the five-turbine Hywind Scotland installation. Tracking the impact of the tow-to-port approach across the globe was the objective. Heavy tugboat activity and handling of the cables raised underwater sound levels up to 29 decibels. The vocalization detections in the area decreased by 33 percent.
What happens when floating wind turbines head to port for repairs
Floating wind platforms are anchored to the ocean floor with heavy anchors attached to the cables. Fixed-bottom turbines, on the other hand, are driven directly into the ground. Operators perform major mechanical overhauls whenever they are needed. Crews disconnect the whole structure and tow it to a deep-water port.
To test this process, researchers used advanced hydrophones and acoustic click detectors around the 30-megawatt Hywind Scotland project in the North Sea. The monitoring array recorded sound levels and marine mammal activity at all five turbines down to 395 feet deep in the water.
Disconnecting the floating platforms caused great disturbances to the marine environment for some distance around the activity. Sounds, or, more accurately, shockwaves, from breaking up the platforms were transmitted across great distances. The recovery of the marine environment from the disturbance created by the vessel is reasonably rapid.
The underwater noise spike that operators never expected
Harbor porpoises are often found in Norwegian waters and depend on their hearing for most of their other senses.
Because equipment calibration limitations precluded reporting absolute broadband sound pressure levels, the study measured relative acoustic changes rather than absolute decibel values. Results showed that sound levels rose significantly during major maintenance, peaking at up to 29 dB above routine operational averages. During operation, the vessel transferred acoustic energy into the water at a level 800 times greater than the ambient level.
Scientists tracked a steep drop in marine life activity within 1.2 miles of the project site during peak noise generation. Acoustic detections at monitoring stations up to 1,970 feet away dropped 33 percent during turbine activity. This portion of the local population left the area for a short period of time to escape the noise created by the vessels.
The hunting efficiency of animals that continued to stay in the wind farm was not reduced, according to the data. Successful prey hunting continued around the floating foundations. Acoustic recordings confirmed that feeding buzz ratios remained consistent.
The simple reason why ocean life returned so quickly
The results show that tow-to-port maintenance does not lead to permanent habitat avoidance, because porpoises returned to the project area just minutes after vessels left. Hunting success stayed consistent around the floating foundations throughout the maintenance period.
Tow-to-port operations remain dramatically quieter than traditional fixed-bottom construction. Fixed-bottom construction relies on seafloor pile driving that can cause severe acoustic trauma for marine mammals. Floating turbine maintenance relies on vessel thrusters rather than impact hammering.
Upcoming commercial projects planned for the late 2020s will feature dozens of massive turbines across much wider expanses of the ocean. Scaling up turbine numbers will inevitably increase vessel traffic and extend maintenance schedules. Commercial facilities could end up generating prolonged acoustic disturbances across broader marine areas.
Environmental impacts from floating wind turbines may not be as extensive as we thought
The report concludes that tow-to-port maintenance represents a manageable environmental trade-off for deep-water clean energy. By staggering turbine repairs outside peak breeding seasons and coordinating vessel movements, operators can minimize underwater noise. They can also protect sensitive marine wildlife, and ensure the sustainable growth of global floating wind energy.
All the details of the study can be found here: Caitlin B Harris, Steven Benjamins, Nienke van Geel, Ellen White, Beth Scott, Benjamin J Williamson, Impacts of large-scale maintenance of a floating offshore wind farm on noise levels and harbour porpoise activity, ICES Journal of Marine Science, Volume 83, Issue 8, August 2026, fsag150, https://doi.org/10.1093/icesjms/fsag150
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