Currents are responsible for circulating water throughout the earth’s oceans.
This lesson will discuss surface ocean currents, deep water ocean currents, and the forces that drive them.
Definition of Ocean Currents
Imagine you fill a bathtub with cold water then add hot water at one end. You will not have warm water until it is mixed. Put your hand in the hot water and push it toward the cold end of the tub. You can feel the movement and the difference in water temperature.
You created a small current in your bathtub by causing the water to move from one place to another.Much larger currents are at work in our oceans, circulating water around the world. These ocean currents, which are massive currents that are influenced by a variety of different forces that act to propel the water both on the surface and in deep ocean waters. This movement has a significant effect on the earth’s weather. For example, the Gulf Stream current carries warm water toward northern Europe.
Due to this, coastal countries in northern Europe have a milder winter than coastal areas in the northeast United States that are much farther south.
Currents found in the upper 1,300 feet of the ocean are called surface currents. Let’s examine some of the forces that determine the direction of these currents.
GravityThe surface of the ocean is not even. Due to this, gravity has an impact on the flow of water in the ocean. The earth’s gravity pulls at water, causing it to flow downward from higher surface levels. You will notice the impact of gravity as it is mentioned alongside various other forces throughout this lesson.
WindWind is the driving force behind our oceans’ surface currents. In other words, most surface currents are caused by wind, which has the greatest impact on these currents. As the wind blows over the water’s surface, it produces friction. This friction pushes the water along and forms a current moving in the same direction the wind is blowing. The current will continue in the direction of the wind until other factors – such as nearing a land mass or colliding with another ocean current – cause the water to build up and move in different ways.Coriolis EffectThe spinning of the earth deflects movement. This is called the Coriolis Effect .
We usually see no impact from the spinning of the earth, but we do notice its effect on surface currents because they are large and move over long distances. The Coriolis Effect comes into play when water being pushed by the wind piles up into mounds. As gravity pulls the water down the slope of the mound, the Coriolis Effect forms a current that creates spiral patterns called gyres that help push the current forward. These gyres move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.Continental deflectionWe briefly mentioned earlier that nearing a land mass is one factor that causes water to build up and change direction.
When water building up or changing direction occurs near a very large land mass, or continent, it is called continental deflection. Since the earth is not completely covered in water, continental deflection plays a large role in the overall direction of surface currents. The water can’t travel over or through the continent, so it is forced to move around it.
Deep Water Currents
When you drop about 1,300 feet below the surface, deep water currents move the ocean’s water. These currents move much slower, and the forces that drive deep water currents differ from the forces that drive surface currents. These currents are caused by density differences that exist due to the water’s temperature and the amount of salt in the water.
This is called thermohaline circulation, ‘thermo’ referring to the temperature and ‘haline’ referring to salt. Cold water holds more salt than warm water. The salt content makes it more dense, or heavier, than the warm water. Gravity now comes into play as the warmer, lighter water rises and colder, heavier water sinks.
It sounds simple, but there is a bit more to it. As the warm water rises, cold water is pulled up to fill in the space left behind. The opposite is also true. When cold water sinks, warm water is pulled down to fill in the space left behind. Thermohaline circulation is also known as the Global Conveyor Belt because this process acts to move water throughout the entire ocean, distributing nutrients as well as regulating temperature and salinity.
Water current is the movement of water from one place to another. Ocean currents are massive currents that are influenced by a variety of different forces that act to propel the water both on the surface and in deep ocean waters. Surface currents are found in the upper 1,300 feet of the ocean. Most ocean currents are caused by wind pushing the water along.Other factors then come into play and direct the flow of surface currents. Continental deflection can cause redirection of water as it builds up to a higher level as it nears land and is forced to change course. Gravity then pulls the water downward, altering the direction in which the current flows.
Since there is so much water involved and it is moving for a large distance, the rotation of the earth even has an impact because of the deflection caused by it, which is called the Coriolis Effect. When gravity pulls water downward, the Coriolis Effect creates spiral patterns that help push the current along which are called gyres.Deep water currents move the ocean water below 1,300 feet. Thermohaline circulation is caused by caused by differences in water temperature and salt content and the movement that is produced by these differences. As the heavy, colder water sinks and warmer, less dense water rises, water is moved throughout the entire ocean.
This has given these deep water currents the nickname ‘Global Conveyor Belt’ because this process acts to move water throughout the entire ocean, distributing nutrients as well as regulating temperature and salinity.