When you picture the Arctic, you probably imagine snowy landscapes, polar bears,
and frolicking marine creatures, largely untouched by humans. But unfortunately,
even the remote Arctic isn’t safe from pollution.
And I'm not just talking about the plastics and chemicals that get swept up by currents
and dumped in the Arctic Ocean... although those are also not great. There's a different kind of
pollution that's increasing in the Arctic, and it's completely invisible: noise pollution.
As there has been less and less ice in Arctic, more and more cargo ships
have been pass through this area, and their rumble is driving some marine
species from their homes and making it nearly impossible for others to communicate or hunt.Understanding why noise pollution is such a problem,
Understanding why noise pollution is such a problem, and how we can fix it, is key to protecting the Arctic’s entire ecosystem.
[Intro music]
To be clear, noise pollution doesn’t just affect the Arctic. It’s been a
growing problem all over the world for decades.
These days, there are tens of thousands of merchant ships at sea every day. They move
tons of important things around the world, like food, oil, tech products, and clothes.
But until recently, the Arctic Ocean was kind of a quiet oasis. Ships mostly
steered further south because the Arctic ice cover made it too dangerous to pass through.
The thing is, that’s changing now as the Arctic ice melts due to climate
change. More and more ships are taking shortcuts through the Arctic Circle,
and ecosystems that had stayed pretty quiet are suddenly full of noise.
For species that are already facing a warming ocean and reduced polar ice surface,
this noise is making a bad situation even worse.
What makes this problem complicated is that noise pollution from ships comes in many forms,
so it’s not as easy as just putting a muffler on the back of the boat.
Their engines do make noise as they burn fuel. But different kinds of machinery
are also constantly rattling against the hull, which sends vibrations into the sea.
And the part of the ship that typically makes the most noise isn’t the engine
itself – it’s the propeller. As propellers turn through the water,
they create bubbles that pop in a process called cavitation.
And when ships are moving /fast/, all those popping bubbles get especially loud.
You might not think of popping bubbles as especially noisy,
but on some ships, cavitation can be louder than a motorcycle roaring by,
and the sound is /constant/ while the propellers are turning.
In the Arctic, there’s also one more big factor:
Many ships have to use icebreakers to carve a path through the frozen top layer of ocean water,
and as you might guess, those icebreakers are… not quiet.
All this mechanical noise radiates into the sea at different frequencies,
and it messes with marine life in a /bunch/ of different ways.
For one, low frequencies can travel hundreds of kilometers underwater,
so the low rumble of ships becomes part of the ambient noise of the sea.
Between 2013 and 2019,
noise levels produced by merchant ships /doubled/ in some parts of the Arctic.
All this noise makes it harder for animals to communicate underwater. It’s like trying to
talk to someone at a concert or in a crowded restaurant. Voices just get drowned out.
And that’s bad news for some marine animals, like the Arctic’s beluga and bowhead whales,
because they use sound to communicate over dozens or even hundreds of kilometers.
Whale songs are made up of a variety of noises, it got clicks, whistles, and pulses,
although we’re still decoding exactly what it is they’re saying in these songs.
But we do know that they sing at a very low-frequency,
which allows the songs to be heard over those long distances.
In some Arctic waters, their sounds can travel especially far. That’s
because sound changes speed depending on the density of the water it’s traveling through,
and that density of water depends on a whole host of factors. So as the sound waves hit
layers of water with different temperatures or salinity levels, or even schools of fish,
the sound refracts, or bends – like when you put a straw in a glass of
water and it’s changing direction? In some areas, this effect creates
a kind of pipeline that actually channels some whale songs across vast distances.
This long-range communication is /critical/ for whales.
If they can’t hear each other, it’s harder for them to navigate together and find mates.
Those bowhead whales have actually changed the way they use their voices to hear each other
over the noise, by calling louder and more frequently to try to be heard over the din.
And at a certain noise threshold, they stop calling to each other altogether.
Researchers studying their surface behaviors even report that the whales
spend less time breathing at the surface to avoid all the noise.
On top of this ambient noise, marine animals can also hear
the higher frequencies produced by individual ships passing close
by that go unnoticed by those of us on land. These sounds can be much louder,
and research shows they can boost animals’ stress levels and even injure their hearing.
Studies have found that fish like the Arctic cod have actually moved out of their native
ranges altogether to avoid ship noise, meaning that the animals who ate those cod,
like ringed seals and beluga whales, need to find other sources of food.
The Arctic is also home to some species of dolphins, including killer whales,
that use echolocation to find prey underwater. When it gets too loud,
the ship noise can drown out their clicks and make it harder for them to find food.
The bottom line is that many Arctic animals rely on hearing to hunt,
communicate, or find their way through the water, and this noise affects all of them.
To make matters worse, as the Arctic gets warmer, sound is likely to travel more easily,
partly because there won’t be as much ice around to scatter the sound waves.
So, scientists are eagerly working on solutions. And the good news is,
there are a lot of ways that we can turn the volume down in the sea!
For one, just slowing down can go a long way. The slower ships go,
the less their propellers need to turn, which produces less noise.
And we’ve already been able to see how slowing down can make a big difference.
At Canada’s Vancouver Island, researchers working on the Enhancing the Cetacean
Habitat and Observation Program, or ECHO, requested that passing container
ships reduce their speed while passing through the Haro Straits.
They found that the merchant ships that slowed
down by just 5 kilometers per hour were able to cut their noise in half.
But there are also engineering solutions that can make ships quieter. For instance, changing
the shape of the propeller blades can reduce cavitation and keep those bubbles to a minimum.
And some solutions are as easy as drilling a few holes in the propeller blades. It turns out
that drilling holes at optimal points along the blade prevents the formation of those bubbles by
reducing the pressure at the blade’s edge, all with a minimal impact on propeller efficiency.
Ships’ hulls can also be designed to make more consistent wakes,
which not only reduces noise itself but also helps the propellers perform better,
and improved performance means quieter performance.
Noisy machinery can also be connected to the ship by springs that absorb vibrations. When
a piece of vibrating machinery is connected to a spring, the spring will compress and bounce back.
That keeps the vibrations from reaching the ship’s hull and passing through to the water.
These days, there are even computer models that can test the so-called noise footprint
of a ship before it is built, so engineers can design ships with sound pollution in mind.
All of this can drastically reduce the amount of noise pollution ships add to the open sea,
and ultimately help to protect our planet’s wonderful marine creatures.
So far, though, most measures to reduce noise have only been adopted on a voluntary basis.
These technologies aren’t yet being widely used, and there’s a lot that still needs to be done.
For most of history, we just weren’t thinking of noise pollution when we
designed ships or mapped shipping routes. But now, we have a chance to do better.
As melting ice opens up more pathways through the Arctic Circle and sounds travel more freely across
the ocean, we need to take steps to protect nature from the damage caused by the noise.
Fortunately, cleaning up that racket is nowhere near as messy as cleaning up an oil spill or
the Great Pacific Garbage Patch, and it’s something we already have the power to do.
This video was made in collaboration with BBC Studios Natural History Unit.
Their initiative, Our Frozen Planet, brings you urgent stories about the
effects of climate change around the globe, and accounts of the people
dedicated to championing positive change to protect the future of our planet.
Thanks to the Natural History Unit for collaborating with us on this video. Head
over to bbcearth.com/our-frozen-planet to find out more, there is also a link in the description.