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.