L1 introduction to oceans

IB Oceans and their Coastal Margins

B1 – Introduction to Oceans

World’s Oceans

Distribution of Oceans• The world’s oceans are referred to collectively

as the “world ocean”.• Boundaries that separate the oceans are

arbitrary and blurred.• Size of oceans varied from largest to smallest:– Pacific– Atlantic– Indian– Southern– Arctic

Water in the Oceans

• Volume – 1.185 billion cubic kilometres• 97.3% of all water on the planet.• Chemical composition of water in each of the

oceans is very similar from place to place -> varies little from year to year.

• Inputs to Ocean Water– Water (from rivers, glaciers, rain)– Chemicals (dissolved mineral

Ocean Currents

Two types of ocean currents:• Surface Ocean Currents• Deep Ocean Currents

What do currents do?• Regulate the world’s climate.• Important for marine life.

• Ocean currents occur because there is very little friction between the ocean waters and the solid earth.

• As the earth rotates the water moves differently to the solid crust and the lighter atmosphere.

• Surface currents move at 9km per hour, deep currents move at 1km per hour.

Deep Ocean Currents

Deep Ocean Currents

• Deep Ocean Currents occur between the ocean bottom and 400m below the surface.

• Created by difference in water density.• Cold or salty water is more dense than warm

or less salty water.• One cycle of the ocean conveyor belt can take

1,000 years to complete.

Surface Currents

Surface Currents• Surface currents are driven by the wind.• World’s prevailing winds create giant circular

currents in the major ocean basins.• Subtropical high pressure areas at 30 degrees

latitude. • Combination of friction and coriolis force water does

not create exactly parallel to the wind direction.• Coriolis Force – created by the rotation of the earth. – Water pulls to the right in the northern hemisphere– Water pulls to the left in the southern hemisphere.

Major Ocean Currents

Ocean Gyres

Gyre – any large system of rotating ocean current.

Gyres are caused by the Coriolis effect – planetary motion along with friction.

There is a major Gyre for each ocean system.

Ocean Currents Affect Temperature

• Warm Currents carry water Polewards and raise the air temperature of the maritime environments where they flow.

• Cold currents carry water towards the equator and so lower the temperature of coastal areas.

• Main ocean currents follow a circular pattern.

What is this image showing? Why?

Questions

1. Why does the chemical composition of the oceans remain fairly constant over time? (hint: think inputs / outputs)

2. Outline the impact of ocean currents on the climatic differences between the eastern and western sides of continents.

www.oceanmotion.org