Downsides of offshore wind – operating noise

14 MW Wind Turbine

Most of the attention to offshore wind-farm noise has been focused on noise from pile driving and installation. But when you install a large piece of moving equipment somewhere, it is bound to make noise of some sort or other.

There have been a number of published papers addressing the noise contribution of offshore wind farms to the underwater soundscape, but so far these have just been quantitative – how much noise and at what frequencies. In a number of cases the contributed noise does exceed the regulatory threshold for exposing marine mammals to continuous noise (120dB re:1µPa).

Of course this continuous noise threshold was “somewhat” empirically derived because there were noticeable behavioral impacts in marine mammals exposed to noise at that level. But we also know that “sub regulatory threshold” behavioral responses have also been noted in Bowhead whales, leading to the understanding that there may be secondary behavioral thresholds – that an animal will hear a quiet noise, and respond to it. This stands to reason; animal hearing is tailored to respond to important audible signals, even quiet ones.

The “continuous noise exposure threshold” was actually a late-comer in the legacy of noise exposure regulations. The initial regulations had been built around impulse, or intermittent noise (e.g. pile driving and seismic surveys) and noise exposures that would induce a physiological effect – temporary, or permanent auditory threshold shifts. And with that, of course, behavioral responses.

This lower continuous noise threshold is also somewhat arbitrary; it can be adjusted to accommodate for ambient noise levels – as it is not uncommon for a wind-whipped sea, or a loud aggregation of fish to exceed that threshold. But as I have always maintained, the quality of the sounds has more bearing on disturbance than the quantity (I would much rather be exposed to a noisy waterfall than a noisy refrigerator).

So this is the point in evaluating how continuous noise from windfarm impacts marine life; if we are subjecting large areas of marine habitat to continuous noise, even if it is below “regulatory thresholds,” what might we expect?

An important paper by Susan Parks and Rosalind Rolland correlated continuous background noise from shipping with stress in N. Atlantic right whales. Additional research correlates behavioral and biological impacts of noise exposure in marine invertebrates. So if we’re going to power our energy-hungry economy with extensive offshore wind farms, we are bound to see noise-induced habitat changes.

Will these changes be acceptable over the long term? At this juncture I would argue that they’ll be more acceptable than the global impacts of continuing to power our economies with fossil fuel.

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Frank Buffum
Frank Buffum
3 years ago

headline is fuel for naysayers. “Evaluating Downsides…” would me it a notch harder to generate a negative narrative based on headline-only thinking. Think of the splash screen behind a ranting Fox News commentator that shows three headlines splayed behind them as they say “even the radical left admits this is a terrible idea…”