How Ocean Currents Shape Life and Climate Across the World

When I'm not making videos for Khan Academy, I research wildlife on islands. In particular, some of my research takes place on the small isolated islands of Midway Atoll and the North Pacific Ocean where over a million albatross return to breed each year and it is crowded and noisy here. These seabirds spend almost 95% of their life soaring throughout the North Pacific Ocean eating squid and flying fish eggs. And as it turns out, a shocking amount of plastic floating in the ocean. But how does that plastic even get there? Most of the plastic that albatross and other seabirds accidentally eat comes from the mainland, but is transported to the ocean by currents. Ocean currents can be at the surface or deep

underwater. These currents connect to one another as well as to other currents which are affected by global wind patterns, Earth's rotation and Earth's land masses like continents and islands. When these currents connect, they form giant loops called gys. And together, these gys work to drive the ocean conveyor belt, which circulates or moves water around the entire world. Water has a high specific heat capacity, which means that it's pretty good at holding on to heat it absorbs from the sun. So, as the water in our oceans moves around the world, it also carries heat, which greatly affects the world's climate by spreading heat energy. In addition, our ocean conveyor belts helps to maintain

salinity, which is what makes ocean water salty, and nutrients in oceans. And we use these gys, too. Understanding the flow of currents helps us to understand how to use those currents to our advantage for sea travel, fishing, or shipping cargo. Even predicting the path of hurricanes. Although these gys help to circulate ocean waters, they're also pulling in pollution and marine debris or trash that we release in coastal areas. The circular motion of the gy draws debris into the stable center where it becomes trapped. You might have actually heard of the Great Pacific Garbage Patch, which is in the North Pacific Gy. It's actually not a floating island of trash, but it's more of a soup with lots of

plastic suspended in it. Some of it very small, almost the size of a grain of sand, and some of it really large, like nets and fishing gear. Whether this plastic is consumed or wildlife gets caught in it, marine debris is a big problem in our oceans. Beyond plastic though, there's much more to our oceans. There's a whole world of life under the surface. About 25% of all marine life can be found in coral reefs, which are unique habitats formed by corals and often called the rainforests of the sea. In fact, 50 to 80% of the oxygen on Earth is produced from plankton in the ocean, more than we get from trees. But as you descend into the ocean, it quickly becomes dark. Sunlight can reach

about 200 m below the surface or about 600 ft. Beyond this point, small organisms like algae can't photosynthesize or create food using light and oxygen. In addition, as you go further down into the ocean, temperatures fall and the pressure increases. And the oceans are deep, like really deep. In some areas like the Mariana's Trench, the ocean can extend for thousands of feet where the pressure is so great and the temperatures are so low you can't imagine that anything could survive there, especially since there's no light that can reach these depths. But you'd be wrong. Organisms living in the deep ocean must be adapted to survive under extreme pressure, limited light, cold temperatures, and

other factors. Although life is sparse, there is life far deep into the oceans, including scavengers, which eat any carcasses or bodies of dead animals that float down from higher up, like whale carcasses. There's also unique tube worms that survive near hydrothermal vents where superheated water rushes up from deep inside the Earth. Oceans cover the great majority of our planet, over 70% of Earth's surface, and we depend on oceans for much of our day-to-day life. We rely on oceans as a major food resource. In fact, fish and other marine food sources are part of the diet for nearly 3 billion people. We also rely on other ocean resources like oil reserves beneath the ocean, which we use for

powering everything from our cars to our homes. We use oceans for shipping goods all over the world and for traveling, too. Remember the albatross that I mentioned earlier? They can also be an indicator species, sort of like a canary in a coal mine, and they can signal to us when there's a problem in our oceans. Finding plastic in an albatross's stomach tells us that we're having a huge impact on our oceans. with trash from thousands of miles away ending up in these seabirds. It reminds us that even though the oceans are enormous, they're all connected through the ocean conveyor belts, which means that we are all connected. So, what happens in one ocean can affect what happens in another

ocean. Let's work together to protect the oceans and all of the amazing creatures that live there.