Deep Currents
cK-12
7th Grade Informational Reading Texts
Seawater is always on the move. Water that comes up to the surface from deep is rich with nutrients. Plankton gather where nutrients are plentiful. Small fish come to eat the plankton. Of course, larger fish and birds come to eat the smaller fish. So upwelling is responsible for an abundance of life.
Currents also flow deep below the surface of the ocean. Deep currents are caused by differences in density at the top and bottom. More dense water takes up less space than less dense water. It has the same mass but less volume. Water that is more dense sinks. Less dense water rises.
Water becomes more dense when it is colder and when it has more salt. In the North Atlantic Ocean, cold winds chill the water at the surface. Sea ice grows in this cold water, but ice is created from fresh water. The salt is left behind in the seawater. This cold, salty water is very dense, so it sinks to the bottom of the North Atlantic. Downwelling can take place in other places where surface water becomes very dense.
When water sinks it pushes deep water along at the bottom of the ocean. This water circulates through all of the ocean basins in deep currents.
Sometimes deep ocean water rises to the surface. This is called upwelling. Strong winds blow surface water away from shore. This allows deeper water to flow to the surface and take its place.
When water comes up from the deep, it brings a lot of nutrients with it. Why is deep water so full of nutrients? Over time, dead organisms and other organic matter settle to the bottom water and collect. The nutrient-rich water that comes to the surface by upwelling supports many living things.
upwelling also takes place along the Equator. Winds blow the surface water north and south. This leaves a void that deep water can upwell into. The nutrients rise to the surface and support a great deal of life in the equatorial oceans.
Currents also flow deep below the surface of the ocean. Deep currents are caused by differences in density at the top and bottom. More dense water takes up less space than less dense water. It has the same mass but less volume. Water that is more dense sinks. Less dense water rises.
Water becomes more dense when it is colder and when it has more salt. In the North Atlantic Ocean, cold winds chill the water at the surface. Sea ice grows in this cold water, but ice is created from fresh water. The salt is left behind in the seawater. This cold, salty water is very dense, so it sinks to the bottom of the North Atlantic. Downwelling can take place in other places where surface water becomes very dense.
When water sinks it pushes deep water along at the bottom of the ocean. This water circulates through all of the ocean basins in deep currents.
Sometimes deep ocean water rises to the surface. This is called upwelling. Strong winds blow surface water away from shore. This allows deeper water to flow to the surface and take its place.
When water comes up from the deep, it brings a lot of nutrients with it. Why is deep water so full of nutrients? Over time, dead organisms and other organic matter settle to the bottom water and collect. The nutrient-rich water that comes to the surface by upwelling supports many living things.
upwelling also takes place along the Equator. Winds blow the surface water north and south. This leaves a void that deep water can upwell into. The nutrients rise to the surface and support a great deal of life in the equatorial oceans.