Currents and Waves

The water in the ocean is always moving.

A current is water within the ocean that is always flowing.  Currents help to move water around the oceans. Current is caused by things such as temperature, salt in the water, and wind speed.

A wave is a surface current.  Waves make up only a small amount of the currents that are found in the ocean.  These currents are caused by wind that blows across the surface of the water.

Ocean Movements

When water is in the ocean, it is constantly moving.  A current is when the water is moving horizontally.  There are two main types of ocean currents:

  • Surface Currents
  • Deep Water Currents

Ocean surface currents

Surface Currents

When there are currents that are happening on the surface of the water, this is a surface current.  A surface current usually happens on the top 1,300 feet of the water in the ocean.

These currents are what we see when we see waves washing ashore on the beach.  The waves of the surface currents happen when the wind blows on top of the water and causes friction.

Friction is like when you rub your hands together and it causes your hands to get hot.

When the friction of what wind hits the top of the water, it causes energy.  The energy makes waves to flow up to the beach.

When the wind changes, the surface current will most likely change as well since a surface current is caused by the wind.


Scientists say that a wave is called a transfer of energy.  Waves that are found in the ocean are mechanical waves because they travel through the water.  Even though it looks like the wave is traveling with the water, this isn’t true the wave is only moving in an up and down fashion.  When the energy hits the wave, it is what causes the wave to travel.

Types of Waves

There are two different types of waves:

  • Mechanical Waves-These waves are waves that have to have something to travel through.  These waves move when the water molecules run into energy.
  • Electromagnetic Waves-These waves can travel even if they do not have a matter to travel through.  These waves include things such as x-rays and radio waves.

Transverse Waves are the water waves that move in a perpendicular motion.  These waves move left and right while the waves look like they are moving up and down.


A swell is a wave in the water that travels a long distance.  These happen when there is a storm that is coming.  These waves are smooth waves and are not choppy.  The waves that are choppy are caused by the winds.

Scientists can measure how big a swell is by measuring from the crest, which means the top of the wave, to the trough, which means the bottom of the wave.

Deep Water Currents

A deep-water current is when a current happens below 1,300 feet of the water in the ocean.  These currents happen when the temperature of the water changes or when the salinity of the water changes.

Ocean waves

Salinity means the amount of salt in the water.

When the water is heavy, the pull of the moon and the sun causes gravity and it can cause tides to happen in the ocean.

These currents happen in a motion that is circular, and this is because of how the Earth is always rotating.  This causes the currents to move in a clockwise motion in the northern hemisphere and in a counterclockwise motion in the southern hemisphere.  This is called the Coriolis Effect.

Deepwater currents are affected by two things:

  • Primary forces are solar heating, Coriolis Effect, Gravity, and winds.
  • Secondary Forces-where the currents flow.

Solar heating can cause the water to get bigger and water that is near the Equator is higher than other places.  This can cause the water to move at a slope.

When the wind blows across the water for ten hours, it causes the water to flow at 2% of the speed of the wind.

Gravity pulls the water down and causes there to be a water hill.

The Coriolis Effect causes the water to move in the right direction around the water hill.

Coriolis Effect

The Coriolis Effect just tells us that the rotation of the Earth causes the ocean current to travel in different directions.  In the southern hemisphere, the current will travel in a counterclockwise motion.  In the northern hemisphere, the current will travel in a clockwise motion.

Global Ocean Conveyor Belt

When the water is constantly moving in the deep waters, this is sometimes called the Global Ocean Conveyor Belt.  With this movement, the cold, salty water is heavier, and it sinks to the bottom of the ocean while the warm water is not as heavy, and it goes on the surface.

The Global Ocean Conveyor Belt starts in the Norwegian Sea where the water is warm from the Gulf and it heats the water that is cooler in the northern hemisphere.  The cooler water sinks to the bottom and moves south so that the warm water can come in.

The water that is cold flows south to the Equator and then down to Antarctica.  The cold water then goes back to the surface and will mix with the warm water and this is called the Global Ocean Conveyor Belt.

How Do Currents Affect the Climate?

Ocean currents can change the Earth’s climate.  When the water is warm, it means that it is moving from the Equator to other areas in the region, some being cooler.  When this warm water from the Equator hits the cooler water, it causes it to be warmer.

The ocean currents

How Does the Temperature Affect the Current?

When you look deep in the surface of the ocean, you will see that the deep parts of the ocean can be much cooler.  In fact, in the Atlantic Ocean, the water sometimes freezes below the surface.

When the water freezes, the salt from the ocean goes deep into the ice and it will cause the water to get heavy and to sink to the bottom.  This cold water will sink to the bottom and move very slow.  After it moves around for so long, it will reach warm water again and this will cause the water to come back to the surface.

Currents and Waves Facts for Kids:

  • The largest wave ever recorded was 1,720 feet tall in Alaska.
  • Waves transport energy and not water.
  • Surface currents help sailors to be able to sail their ships.
  • Some marine animals use the currents to lay their eggs.
  • All the water in the ocean moves around the world.
  • When a current swirl’s, it is called gyres because it is like a giant whirlpool.
  • Water that is in the tropics is warm and the wind will drive this water to the cooler water.
  • When there is a storm, the water sometimes moves in the opposite direction.
  • When waves hit each other, it can cause huge waves to form.
  • Waves that are huge are called rogue waves.  These waves are caused by wind.

What Did You Learn?

  • What is the ocean current?
    An ocean current is when water is constantly moving in a circular motion under the surface of the water.
  • What is a wave?
    A wave is when the water is moving on the surface of the ocean.  We see waves moving that wash up on the shore of the beach.
  • What direction is a wave moving?
    Even though it looks like a wave is moving forward, the wave is really moving left and right, and the energy is causing the wave to move forward.
  • What causes deep water currents?
    Deepwater currents are caused by how salty the water is, the gravitational pull of the moon and the sun, and the temperature of the water, to name a few.
  • What is the Coriolis effect?
    The Coriolis effect is when water moves in a certain direction in the northern and southern hemispheres.  It moves clockwise in the northern hemisphere and counterclockwise in the southern hemisphere.