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  • 00:00:13,880 --> 00:00:17,851 In the 21st century, you don't have to go that far for fresh water.

  • But still, supply is running out.

  • What if a trip to the well, and a trip to the beach

  • were one and the same?

  • This is 'What If,'

  • and here's what would happen if all sea water became fresh water.

  • The first big question we have to ask is,

  • Well, it wasn't always like that.

  • About 3.8 billion years ago,

  • Earth's surface had finally cooled to the point that water vapor turned to liquid;

  • no salt added.

  • That's right! A really, really long time ago, the oceans were fresh water!

  • But that wasn't going to last.

  • Whenever it rains, carbon dioxide from the air dissolves into the falling water.

  • This makes the rain slightly acidic, and when it falls, it causes rocks to erode.

  • From there, rainwater slides towards nearby rivers and streams,

  • taking loose salt and minerals along with it.

  • From there, this runoff flows from rivers into the ocean.

  • Add to that any additional salt and minerals

  • that would be expelled from hydrothermal vents or submarine volcanoes,

  • and then consider that this whole process

  • has been recurring more or less consistently for 3.8 billion years.

  • That's a lot of salt!

  • In fact, there's so much salt in the ocean,

  • that if you spread it evenly across all the land on Earth,

  • it would amount to one towering layer of salt that's 40 stories tall!

  • And we've got to assume it's for a reason.

  • Freshwater oceans sure do sound like a godsend.

  • A sea without salt would decimate marine life

  • and dramatically affect our weather and temperatures,

  • making human life on Earth very difficult, if not impossible.

  • and as many as 2 million more to be discovered.

  • But if the ocean were to become desalinated, we'd never find them.

  • Saltwater fish, and other ocean creatures

  • evolved to be able to drink salt water to stay hydrated,

  • and get rid of excess salt.

  • Not all sea creatures do this the same way, but,

  • being able to pump out excess salt

  • is crucial to surviving in the ocean.

  • Some species, like salmon, have adapted to tolerate fresh water and salt water.

  • But for the most part, all saltwater species would perish.

  • This includes underwater algae, which,

  • believe it or not, accounts for half the photosynthesis that occurs on Earth!

  • Photosynthesis plays a vital role in supplying our planet with oxygen.

  • Since trees and plants convert carbon dioxide from the atmosphere into the air we breathe!

  • So without algae, not only do we get less oxygen,

  • we also have a lot more carbon dioxide in our atmosphere!

  • This intensification of the greenhouse effect

  • would make some parts of the world unbearably hot.

  • You'd definitely notice this intense heat near the equator,

  • since our ocean currents wouldn't be

  • circulating warm water and air the way they used to.

  • Convection currents help warm water from the equator get farther north,

  • while colder water from the north is able to cool hotter areas down south.

  • At the equator, warmer water can carry more salt,

  • so this denser water sinks lower, while cooler water flows over top of it.

  • And in the far north, the water gets cold enough to freeze and form sea ice.

  • Salt gets left behind as the water freezes,

  • and naturally, this makes colder water up north denser,

  • allowing it to sink to the bottom to make room for the incoming warmer water

  • that's worked its way up from the south.

  • Without salt, the whole process breaks down.

  • Earth's extremities would freeze, while weather around the equator would intensify.

  • For one thing, hurricanes would be a lot more frequent,

  • and a lot more deadly!

  • At this point, our weather and our climate

  • would be totally different from how we know it now!

  • How long would we survive to see all these changes?

  • Not long at all.

  • You'd either freeze, overheat,

  • die in a natural disaster, or starve to death!

  • Yeah, with significantly less photosynthesis,

  • and climates that are either extremely cold or extremely hot,

  • our weather would no longer support the diverse plant life it has now.

  • The entire food chain would collapse.

  • Most species would die off, including humans,

  • since crops we rely on for sustenance would all disappear.

  • So, when we say ocean salinization is important,

  • don't take it with a grain of salt!

  • Of course, we respect the scientific method,

  • so keep questioning the world and its properties, on land and beyond,

  • and come back soon, for another 'What If.'

00:00:13,880 --> 00:00:17,851 In the 21st century, you don't have to go that far for fresh water.

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海の水がすべて真水になったら? (What If All the Sea Water Becomes Fresh Water)

  • 132 4
    Amy.Lin に公開 2021 年 01 月 14 日
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