How Does Ocean Current Work
Hsin Yu Liu
Published: 12/03/2024
In 1992, a cargo ship carrying bath toys got caught in a storm. Shipping containers washed overboard, and the waves swept 28,000 rubber ducks and other toys into the North Pacific (1). But they didn’t stick together -- the ducks have since washed up all over the world. Now you might be wondering, How exactly did this happen? Well the answer is simple- ocean currents.
What are ocean currents?
Ocean currents are driven by a range of sources, such as the wind, tides, changes in water density and the rotation of the Earth. The topography of the ocean floor and the shoreline modifies these motions, causing the ocean currents to speed up, slow down and alternate the direction. The ocean currents can fall into two main categories: surface current and deep ocean currents. The surface currents control the motion of the top 10 percent of the ocean’s water, while deep ocean currents mobilise the other 90 percent, and though they have different causes, surface and deep currents influence each other to keep the entire ocean moving.
1. US Department of Commerce, National Oceanic and Atmospheric Administration. “What Causes Ocean Currents?” Ocean Exploration Facts: NOAA Ocean Exploration, 11 Feb. 2013, oceanexplorer.noaa.gov/facts/currents.html.
How do they work?
Surface currents in the ocean are driven by global wind. Patterns of surface currents are determined by wind direction, Coriolis forces from the Earth’s rotation, and the position of landforms that interact with the currents. Surface wind-driven currents generate upwelling currents in conjunction with landforms, creating deepwater currents. If you zoom out to look at the patterns of surface currents all over the earth, you will see that they form big loops, we call them “gyres”. Gyres will travel clockwise in the Northern Hemisphere and counter-clockwise in the Southern Hemisphere because the Earth’s rotation affects the wind patterns that give
rise to these currents! Unlike surface currents, deep ocean currents are driven primarily by changes in the density of seawater. As the water moves towards the North Pole, it gets colder, and it also has a higher concentration of salt, because the ice crystals that form trap water while leaving salt behind, this cold salty water in more dense so it sinks, and the warmer surface water takes its place, setting up a vertical currant called ”thermohaline circulation”.
Occasional events such as huge storms and underwater earthquakes can also trigger serious ocean currents, moving masses of water inland when they reach shallow water and coastlines. Earthquakes may also trigger rapid downslope movement of water-saturated sediments, creating strong turbidity currents.
The world ocean current
Occasional events such as huge storms and underwater earthquakes can also trigger serious ocean cuAfter understanding the cause of ocean currents and the working system, let’s move on to the world's main ocean currents. The oceans cover more than 70% of Earth, we can divide them into major ocean currents that circulate water in our 5 oceans: (2) rrents, moving masses of water inland when they reach shallow water and coastlines. Earthquakes may also trigger rapid downslope movement of water-saturated sediments, creating strong turbidity currents.
2. Hutchinson, Brian. “The East Australia Current and Sea Turtles - the State of the World’s Sea Turtles: SWOT.” The State of the World’s Sea Turtles | SWOT, The State of the World’s Sea Turtles | SWOT, 24 Oct. 2023, www.seaturtlestatus.org/articles/2010/takin-a-ride-on-the-eac-across-the-southern-pacific-ocean.
Australian Current (EAC) and sea turtle
The ocean currents make the water system flow, but it is also beneficial for the sea animals to travel. Fun fact, have you ever heard of the cartoon “Octonauts - The Leatherback Sea Turtle''? They state that the ocean is a sea turtle highway, it helps them to travel farther in the ocean. New research has revealed that the East Australian Current (EAC) plays a critical role in transporting turtles between habitats across the Southern Pacific Ocean.
2. Hutchinson, Brian. “The East Australia Current and Sea Turtles - the State of the World’s Sea Turtles: SWOT.” The State of the World’s Sea Turtles | SWOT, The State of the World’s Sea Turtles | SWOT, 24 Oct. 2023, www.seaturtlestatus.org/articles/2010/takin-a-ride-on-the-eac-across-the-southern-pacific-ocean.
Tiny loggerhead turtle hatchlings emerge from nesting beaches on the western side of the Southern Pacific Ocean in Australia and New Caledonia, while larger juveniles are often captured in longline fisheries off Peru and northern Chile, on the far eastern side of the Pacific Ocean. So what explains the discovery of the different-sized loggerheads on opposite sides of the same ocean? The key piece to this transoceanic puzzle is found in turtle DNA. The female sea turtle must go back to the place they were born to lay eggs, in this case, the East Australian Current helps them reach their destination faster. (3)
In the end, the significance of ocean currents is demonstrated as it helps the entire ocean flow, with its structural layers allowing marine animals to travel across different oceans.
3. Earthhow. “The Major Ocean Currents of the World.” Earth How, 29 Sept. 2023, earthhow.com/ocean-currents/.
Resources
Hutchinson, Brian. “The East Australia Current and Sea Turtles - the State of the World’s Sea Turtles: SWOT.” The State of the World’s Sea Turtles | SWOT, The State of the World’s Sea Turtles | SWOT, 24 Oct. 2023, www.seaturtlestatus.org/articles/2010/takin-a-ride-on-the-eac-across-the-southern-pacific-ocean.
Earthhow. “The Major Ocean Currents of the World.” Earth How, 29 Sept. 2023, earthhow.com/ocean-currents/.
This episode kinda makes the article less professional in my opinion. Could we remove it?
Octonauts - The Leatherback Sea Turtle | Full Episode 14 | Cartoons for Kids