Quieting the Anthropocene Seas – Part 3
3/2/23 – Some things we can do to reduce acoustic stress in the oceans
For new arrivals to the Field Guide (and there have been quite a few of you lately), you might want to go back to the first of these three pieces on the harms of (and solutions for) human noise in the oceans.
As always, please remember to scroll past the end of the essay to read some curated Anthropocene news.
This week’s piece is a bit long. If your email provider clips it short, please click on the title of the essay and it will bring you to the full piece in the Field Guide archive.
Now on to this week’s writing:
For those of us living in wealthy, high-consumption cultures, one of the hallmarks of this bizarre and tenuous era in human history is our capacity to do great damage at great distances. Despite our concerns and empathies, what we eat, wear, drive, or buy is often extracted at great cost to unseen human and ecological communities. Irrational but powerful global systems are in place to wreak havoc for our benefit, and to the extent that we participate in the culture we are both complicit in, and ensnared by, that havoc.
Usually, a discussion about our capacity to do globalized harm is illustrated by the media, activists, or scientists bringing the story to our attention. The oceans, though, are something of a black box. It’s too dark to see and very few people there to see it. And when the harm is acoustic rather than visual, we might as well be talking about cannon fire on the dark side of the Moon.
Everyone wants a happy, healthy ocean. To get there, though, we have to prioritize oceanic Anthropocene problems alongside land-based climate change and biodiversity loss. It all needs to be on the civilizational to-do list.
The reality is that there is only one global environmental crisis: the rapid and widespread disruption of the community of plants, animals, microbes, and ecosystems of the Earth. A warming Earth is a disrupted Earth. And anyone who thinks we can “solve” the crisis without respecting and attending to the health of the oceans doesn’t know how the planet works.
So much of what must be done to repair our relationship with the oceans has to do with halting greenhouse gas emissions and at least partially reversing climate change. The climate-related “deadly trio” of warming, acidification, and deoxygenation, if allowed to continue at their current pace, is a precursor to a mass extinction.
While that’s going on, though, there are easier tasks to take on in easing our burden on the oceans: managing sustainable fisheries at a habitat scale, strictly reducing pollution from industry, controlling nutrient run-off from agriculture, etc. The easiest task of all, though, is to reduce our noise pollution.
And that brings me back to my list. Last week I discussed seismic airguns and military explosive use. This week I’ll wrap up with sonar, shipping noise, wind power, and small boat noise.
Sonar is an acronym (Sound Navigation and Ranging) for an acoustic technology. Sound waves are emitted underwater by a ship or aircraft and the rate at which the waves return creates a map of the area being scanned. There are different types of sonar, which I won’t get into here, except to mention the difference between active and passive sonar. Active sonar, as I just described, sends out signals and listens for the response. Passive sonar simply listens, like a naval ship listening for an enemy submarine.
Sonar can kill. A sound wave is a physical force which, at its most powerful, can deafen or even rupture lungs and brain tissues, whether whale or human. At 235 decibels (dB), the strongest military sonar can still register at 140 dB – which is the sound of a jet at take-off – up to 300 miles away from its source. The Navy takes the threat of sonar to human divers so seriously that strict protocols, like locking away the keys to the sonar equipment, are in place whenever a diver is in the water near a ship. Alternatively, a naval ship will sometimes use active sonar as a defense against the prospect of an enemy diver.
If the Navy were as attentive to the risks from sonar to marine life, I wouldn’t have as much to say here. Every commercial, private, and research ship in the world carries one or more types of sonar, but the strength of military sonar is quite different. I’ve seen it described as “rolling waves of sound” and “an acoustic holocaust.” According to a 2012 Times article,
the Navy estimates that blasts from its sonars – used in training and to hunt enemy submarines – result in permanent hearing losses for hundreds of sea mammals every year and temporary losses for thousands. All told, annually the injured animals number more than a quarter million.
And a 2021 Guardian article details how Navy activity in the Mariana Islands Training and Testing (MITT) study area has been linked to multiple stranding events by Cuvier’s beaked whales, a deep-diving species. Beaked whales seem particularly prone to sonar-caused strandings, perhaps because the noise causes them to surface too quickly and develop a fatal case of the bends.
It’s not just the military, though. Multibeam sonar used for surveying by both industrial and scientific vessels was found to have caused the stranding of 100 melon-headed whales in Madagascar. The JONAS project, which focuses on the anthropogenic soundscape in the Atlantic, describes the general impact from sonar this way:
As they attempt to flee the sound, stressed animals may alter their diving pattern, which can trigger physiological changes that lead to stranding. The use of active sonar can cause more resilient cetaceans to avoid the area entirely or cease feeding – even when the sound level is relatively low.
Chronic disruption of marine animals’ basic daily functions can only lead to population-level impacts. If feeding, mating, and communication are more difficult, the species suffers. This will be more true for some species than for others, of course, but sonar has long been a major threat to many cetaceans.
What can we do? Unfortunately, there’s no new technology arriving to replace sonar. For industrial and research purposes, intense active sonar should only be allowed when the benefit is extraordinary and precautions are in place. For naval uses, there have to be strict restrictions on when and where the most intense sonar is used, particularly for the protection of marine mammals. There has been some successful litigation on this front, but not enough.
The Navy continues to rely on thin data claiming little harm, when in fact 1) anyone who has studied the ocean knows it takes years of intense research to understand what’s happening, and 2) the capacity of sonar to do harm is well known. Currently, the best Navy protocol in place involves observers on deck during exercises searching the immediate vicinity for a glimpse of a whale or dolphin. To me, this seems about as thorough as scanning the yard for wildlife before setting the entire town on fire.
I’d like to question the necessity of naval war games, but according to a pro-sonar Dept. of Justice write-up, “Mid-frequency active sonar (1kHz-10kHz) is the Navy’s primary tactical sonar and its main tool to combat the threat posed by the world-wide proliferation of ultra-quiet diesel submarines,” and active training is required to develop the “ship-wide and strike-group-wide teamwork necessary to execute modern, coordinated, integrated anti-submarine warfare.”
It would be best if the Navy was at least willing to 1) admit that their intense sonar usage was an active war of attrition against many of the ocean’s large keystone species, and 2) work cooperatively with researchers to meaningfully increase the number of peaceful no-go zones for sonar use.
The worst sounds in the ocean may be from seismic airguns and from military sonar and explosions, but the International Maritime Organization (IMO) admits that most of our “continuous anthropogenic noise in the ocean” is generated by shipping. Remember the recording I provided last week of orca calls in the Port of Vancouver being drowned out by a passing ship? And remember the Marine Traffic map from two weeks ago, and the “oceanic smog” of noise created by the 60,000 commercial ships at sea at any given moment? Now imagine how far shipping noise radiates out from each of those 60,000 ships, how intense it is in the main shipping lanes, and how much of the ocean it covers.
Since truly changing the airgun/sonar/military soundscape in a short time seems unlikely, perhaps the greatest progress in reducing oceanic noise pollution can be made simply in revolutionizing propeller design and updating ship and engine designs.
Hull and engine design do play a small but important acoustic role. The solutions there are straightforward (for naval architects), and while retrofitting is possible the biggest improvements will be made in the design of new ships. But ships exist for decades, so the turnover is slow. The shipping industry needs to reach zero emissions by 2050, which means that new ships built today should all be required to meet low-carbon and low-noise standards.
In the meantime, engine noise can be dampened with vibration control measures and soundproofing in the engine compartment. Better yet, newer diesel-electric or other integrated electric propulsion engines are much quieter than old throbbing diesel engines. (Remember those “ultra-quiet diesel submarines” the Navy is worried about?) Even better, battery-electric systems or solar-powered boats reduce engine noise almost completely.
A cleaner hull (i.e. free of marine growth) will reduce drag and thus reduce the workload on the engine and propeller. But the main influence on noise by hull design is not its shape in the water but how it shapes the flow of water toward the propeller(s).
Which brings me to cavitation, the main culprit when it comes to shipping noise. Cavitation, which is essentially the constant creation and explosion of air bubbles around the churning propeller, also makes propulsion less efficient and degrades the propeller itself. It has been a problem since the earliest propeller-driven ships were built in the 1830s. Propeller technology, oddly enough, hasn’t changed much in that time. Until recently, it’s been constantly tweaked rather than completely reimagined.
Propeller design discussion can be very, very wonky, if you’re so inclined. For my purposes here, I’ll note that shipping companies are under pressure to reduce carbon emissions, so there’s an interest in finding new propeller and propulsion designs that use less energy without losing speed. The good news is that less cavitation means less noise, lower energy use, and more efficiency. The IMO explains that
Cavitation can be reduced under normal operating conditions through good design, such as optimizing propeller load, ensuring as uniform water flow as possible into propellers (which can be influenced by hull design), and careful selection of the propeller characteristics such as: diameter, blade number, pitch, skew and sections.
But big ships need a new generation of quieter propellers. And we need to target the worst maritime offenders, since half of shipping noise comes from just 15% of vessels. There seems to be good news on the horizon, though, as evidenced by announcements of innovations, like these from PressurePores and FishFlow, and in this Ingenia article. And then there’s the romantic option of making the old new again, by returning shipping to its origins in the days of sail.
At the same time, there are other simple solutions to shipping noise that can be established now. These are largely commonsense steps, already proven, that require only a bit of wise policy rooted in ecological awareness and a basic empathy for marine life. These include rerouting ships, reducing activity, or enforcing noise limits in ecologically sensitive areas like Marine Protected Areas and Particularly Sensitive Sea Areas, or at sensitive times like spawning.
The simplest solution for reducing noise might be to slow ships down. The ECHO program in the Port of Vancouver found that “lower ship speeds reduce the underwater noise generated at the vessel source as well as total underwater noise in nearby habitats, potentially improving foraging conditions.” Likewise, one study of Mediterranean shipping between 2007 and 2015 demonstrated that slowing the speed of noisy vessels from 15.6 to 13.8 knots cut noise by 50%. That’s a pretty amazing improvement for dropping speed by less than 2 knots.
Not that we needed more evidence that slowing down the pace of human civilization would benefit the life around us, but there it is.
The era of offshore wind is upon us here in the U.S. We’re years behind China, Europe, and the UK in deployment of ocean-based turbines, with only a handful of turbines in the water now, but the Biden administration aims to take the lead by installing 30 gigawatts (GW) of offshore wind by 2030. For perspective, global ocean-based wind power is at about 50 GW currently.
More interestingly, only 0.1 GW of that 50 GW comes from floating turbines. The Biden plan (including the Wind Shot initiative) calls for all 30 GW to be from floating turbines. You’ll see the good-news relevance of this in a moment.
For an introduction to offshore wind, its place in the Anthropocene landscape, and how it fits into our necessary future, check out Offshore, my wide-ranging essay from a year ago.
As far as making noise, ocean-based wind turbines have two contributions: construction noise (anchoring to the sea floor) and operational noise (from turbines and the ships that service them).
Construction noise for wind turbines is largely from pile-driving the foundations for fixed turbines, and it can be extremely loud – around 220 decibels, more than an oil tanker’s propellers but less than a seismic airgun – and very disturbing to marine life. There are multiple solutions for mitigating construction noise. For the curious engineers and scientists among you, here’s a comprehensive 40-page document from the Federal Agency for the Conservation of Nature in Germany.
For the rest of us, floating offshore turbines are the best solution to construction noise, because construction noise is limited to towing and anchoring the turbines. The type of anchors will define the noise level, but it can be minimal if, say, suction-bucket or gravity-based foundations are used instead of pilings that need to be hammered into the seabed. Gravity-based foundations are really just massive pre-made concrete blocks. To understand suction-buckets, I recommend this video, if for no other reason than to hear the word “suction-bucket” in a Scottish accent.
So far, most ocean turbines are not floating but sitting on a foundation driven into the sea floor. To reduce the extreme noise of pile-driving for large monopile foundations (see the turbine on the far left of the image above) or any other underwater construction, one American company, AdBm Technologies, has pioneered an elegant and affordable solution that dampens noise across the sound spectrum. When paired with a bubble curtain, which eases the noise at higher frequencies, this solution can reduce overall noise by 25 dB. (Remember that perceived noise is cut in half for every 10 dB reduction.)
Assessing operational noise from wind turbines is a bit complicated, but the first thing to know is that turbines are generally much quieter – at least 10 to 20 dB less – than ship noise, and the sound does not carry as far as ship noise. So that’s good news, though it’s safe to assume that wind turbines are having some kind of impact. Looking ahead, as massive wind farms become commonplace and larger turbines are introduced to offshore locations, there is a concern about the cumulative noise.
The noise originates in the gearbox and other machinery in the nacelle (behind the hub of the turbine’s blades) and from wind action on the entire structure. That above-water noise vibrates the turbine and then emanates from the foundation of the turbine. It’s unclear to what extent different kinds of foundations might affect the noise level, because there hasn’t been enough research yet.
“It is very unlikely that operational noise will lead to any injury or even hearing impairment,” one acoustic researcher has said, “but behavioral changes could be a concern.” In terms of marine mammal impacts, it’s known that harbor porpoises seem comfortable coexisting with wind farms, but for whales and other cetaceans their willingness to be near wind turbines is unclear.
The good news is that a) turbines are much quieter than ships, b) newer drive technology in the nacelle is much quieter, reducing gearbox noise by 75%, and c) it’s possible that floating turbines and alternative foundations can dampen turbine noise. The bad news is that a) wind farms are persistent sources, b) new larger turbines are louder than small ones, c) overlapping noise from multiple turbines will likely create louder cumulative sounds, and d) wherever their noise is louder than the natural ambient soundscape they’ll have an impact.
Much more research is necessary to tease out the details of the problems and solutions, but it seems likely that with care the offshore wind industry can be maintained as a minor, if large-scale, annoyance.
SMALL BOAT NOISE
Finally, there’s the noise from smaller boats, whether local diesel-powered fishing boats or small skiffs with outboards. Maybe you have a boat and are wondering how to make it quieter and friendlier? The principles I discussed for shipping noise apply here, especially noise from engines and propellers. And the solutions are much the same: new hybrid or electric motors, and better propeller design.
Two innovations that interest me are the Sharrow toroidal propeller and the Torqeedo electric outboards. The toroidal prop (see picture above) is the first real reimagining of propeller design in the last 180 years. It nearly eliminates cavitation and propeller noise, increases fuel efficiency, improves thrust, etc. It really seems like the revolution we need to remove most propeller noise from the oceans, though I haven’t seen any information on whether they’re usable on large ships. Read this article from New Atlas for videos and more information.
The Torqeedo electric outboard is a good example of what may be coming to transform the outboard industry too. They’re much lighter, simpler, and quieter. If you’re thinking about a new outboard, check out this good, chatty video review of a tiny 3HP Torqeedo outboard for a dinghy.
The problem is cost. The market for this stuff is still small and high-end because it’s not being mass-produced. If you have tens or hundreds of thousands of dollars to throw around, you have plenty of amazing options. For a sample, check out the new SilentJet hybrid diesel-electric engine from Hinckley Yachts.
We need policies and strategies to push the market down to the rest of us. If, for example, California were to pass legislation that phased out loud propeller designs and gas-powered outboards, that might be a big enough lever to eventually boost production and change the noise much of the world makes in the water. For now, the Sharrow toroidal propeller, at $5,000, is being marketed to the deep-pocketed powerboat crowd. Or as they put it, “The Sharrow MX™ Propeller is specifically designed for high-performance on stern drives and outboard motors between 150HP-450HP.” So, not your little 20HP on a 14-ft skiff... Meanwhile, the Torqeedo 3HP outboard is about $3,000, and their 25HP outboard costs $10,600.
In the meantime, any remaining old 2-stroke outboards should really be retired and upgraded to a 4-stroke engine. 4-strokes are much quieter, more fuel-efficient, and much less likely to leak gas and oil into the water. But anyone looking for a new outboard should at least give Torqeedo or its electric competitors a look first. Imagine a quiet boat with no fuel to manage, and a happier marine community beneath your boat.
Even if the science on our noise impacts in the ocean is thinner than policy makers would like, we should act in the best interest of life. At this stage of the Anthropocene, we’re long past the time when we need to wait for the kind of slow, bomb-proof analysis forced upon scientists and society by industries looking to protect their polluting status quo.
The fossil fuel companies have delayed the necessary restructuring of civilization for decades, and that’s time we did not have. Future generations will pay the price that even now is coming due. Regarding our excessive noise in the oceans, as with all our impacts on living communities, we must act based on a commonsense and rational precautionary principle. Why be harmful when we can reduce that harm?
Lots of good work is being done on ocean noise, from NOAA’s Ocean Noise Strategy Roadmap, the International Maritime Organization’s noise guidelines (due to be updated later this year), the Saturn project on underwater noise, and the ECHO program at Port of Vancouver. Alongside the rebound of some whale populations, and efforts to create Marine Protected Areas, reduce ocean pollution, and create an international treaty for the protection of ocean biodiversity, there’s a fair amount of good news for the oceans. But it’s only a start.
“Cutting noise is possibly the lowest-hanging fruit to make a difference and we can change that today,” a marine biologist told the Guardian: “I have real hope that we will hear a healthier ocean in our lifetimes.”
Thanks for sticking with me.
I keep the Field Guide free because our Anthropocene future is a conversation we should all be having. If you can afford a paid subscription, you’ll sustain my work and help keep it free for those who can’t. Please consider becoming a paid subscriber. Thank you!
In other Anthropocene news:
Please help save the Okefenokee Swamp. It’s a vast, dark, magical place, and now threatened by an ill-designed and unnecessary strip mine, as this Times article explains. You don’t have to live in Georgia to comment, so please send a note if you want to help protect one the last great remaining large-scale wetlands in the U.S.
Never underestimate the power of one person obsessed with helping an animal (or a species). From the Guardian, a good-news story about one man’s work to understand and protect the giant armadillo.
Also from the Guardian, despite the recent snow and despite the blip of Arctic weather we in the northern U.S. received in January, this has been a shockingly warm winter for most of the country. For now, the immediate consequences are not for humans but for the flowers and pollinators and other ecological phenomena losing their ancient balance.
From the International Energy Agency, a new analysis shows the grotesque inequality of CO2 emissions: In 2021, the top 10% emitted 48% of global CO2, while the bottom 10% emitted just 0.2%. Read the article for more detail and its excellent graphics.
From Lit Hub, an excellent piece on the great news in whale recovery (for some, not all species). The piece is actually an excerpt of Christopher Preston’s Tenacious Beasts: Wildlife Recoveries That Change How We Think about Animals.
From Phys.org, a new study makes it clear that today’s biodiversity crisis – the steady loss of plants and animals pushing entire species toward extinction – is a precursor to a mass extinction that will wipe out life on Earth, unless we reverse human harm to the natural world. This is not speculation, nor is it alarmism. It is the way the Earth works:
“We are currently losing species at a faster rate than in any of Earth’s past extinction events. It is probable that we are in the first phase of another, more severe mass extinction,” he said. “We cannot predict the tipping point that will send ecosystems into total collapse, but it is an inevitable outcome if we do not reverse biodiversity loss.”
From the Times, poor planning and the antiquated U.S. electricity grid are creating a major bottleneck for renewable energy projects that everyone had assumed would get built this decade. The nation’s climate goals are very much at risk.
What a great series this has been on oceanic noise pollution! After reading the three parts. I feel we're brought up from a starting point of near total ignorance to a level of a good grasp of the problem. No small accomplishment, Jason. Thanks!