Ocean CurrentsGrade Eight Science

Chapter Two

An ocean current is a large mass of moving water in the ocean. A current moves in one, unchanging direction.

There are surface currents (down to about 200m) and deep water currents (deeper than 200m).

Some currents are warm and some currents are cold.

The movement of surface currents is caused by:

wind action

Earth’s spin (Coriolis Effects)

shape of the continentsSurface Currents video http://www.youtube.com/watch?v=YCorkyBe66o

Two currents that affect conditions off the coast of Newfoundland and Labrador (NL) are the Gulf Stream and the Labrador current.

The Gulf Stream is a warm current that begins in the tropics. When it mixes with the cold water in the Labrador current, off the coast of NL, it creates an area where there is a lot of nutrients for fish and marine life. (Grand Banks)

This mixing of warm and cold currents also creates a great deal of fog, especially in the spring.

Cold Labrador Current meets Warm Gulf Stream

The ocean has three layers of water in it.

Surface (mixed layer)– the warmest layer where the Sun’s energy heats the water

Thermocline (200-1000m)– this layer is much colder because less energy from the sun reaches it. Temperatures range from 20 degrees to 5 degrees Celsius.

Deep water (below 1000m)– very cold water with temperatures near the freezing point.

The movement of deep water currents is caused by:

salinity of the water – the more salt there is in water, the heavier it is.

temperature of the water – cold water is more dense than warm water, so it sinks.

In the ocean, masses of cold water sink and travel along the ocean floor. These masses of moving water are called density currents.

Density currents are also caused by differences in the amount of salt (salinity) on the ocean water. Water with a higher salinity is more dense than less salty water.

Video http://www.youtube.com/watch?v=FuOX23yXhZ8

UpwellingThere are currents that move in the opposite direction of density currents.

These currents that move towards the surface are called upwellings.

Winds push surface water away from the coast and cold, deep water moves into replace it.

Upwellings are important because this deep , cold water brings nutrients to the surface .

These nutrients help plants to grow which in turn attracts fish to these areas.

Upwelling occurs off the coast of Newfoundland and Labrador where the Gulf Stream and the Labrador Current meet. This area is called the Grand Banks of Newfoundland and Labrador. This area has nutrient rich water and is a very productive fishing area.

The Grand Banks of Newfoundland and Labrador

• Gyres are ocean currents which move in consistent circular patterns.

• They are made up of two or more currents.

• Gyres move clockwise in the Northern hemisphere and counter clockwise in the Southern Hemisphere.

Five main Gyres of the world’s oceans

Ocean CurrentsGyres

Ocean Currents

There are five major gyres in the world’s oceans:

North Atlantic GyreSouth Atlantic GyreSouth Indian GyreNorth Pacific GyreSouth Pacific Gyre

Gyres

Ocean Currents

There are several factors which all influence ocean currents:

*Temperature*Winds*Continental glaciers*Underwater landforms*Continents*Earth’s rotation*Gravitational pull of both the Sun and the

Moon

Factors that affect ocean currents

Great Pacific Garbage Patch

Ocean Pollution

The Great Pacific Garbage Patch