TEACHER MASTER Water Systems - Science 8

Oceans and Currents – Part 1

Learning Outcomes Addressed

D1. explain the significance of salinity and temperature in the world’s oceans

- define ocean currents

- describe how winds and ocean currents influence regional climates

Recommended time required for this activity: 20 minutes

Corresponding Work from Text:

  • 8.4 Check your Understanding #1-3 pg 234 Science Probe 8

Special Notes:

  • Notes start on the next page so they can easily be made into an overhead
  • This set of notes would be a good lead in to the Ocean Currents Assignment (see Activities)
  • Could lead a discussion as you introduce ocean current section and have some students tell stories about the effects of currents (being pulled out on a floater far from the beach while napping, river rafting, swimming out against the current to try surfing….)
  • When viewing the ocean currents of the world illustration have students come up with trends they see (get them thinking!) For example: The currents seem to be moving in a particular direction, they seem to swirl in an oval or circle throughout an ocean.
  • You could ask students why they think more hurricanes would be observed in areas like Florida? (note where the currents meet)

Try This!

Label the Oceans in the diagram below with the following names:

Pacific, Atlantic, Indian, Southern, Arctic

ARCTIC:

northern portion of pacific and atlantic

ATLANTIC

PACIFICINDIAN

SOUTHERN :

southern portion of all oceans

Oceans are simply water that has collected over time (hundreds of million of years) in the low points of the earth’s surface called basins.

Why is it important for us to study oceans?

  • Oceans are the main reason that life is possible on this planet because they
  • Control the earth’s temperature (plants and animals would not be able to survive if the temperature changed dramatically)
  • Create weather patterns which keep the water cycle going
  • Are the source of all water which supports all forms of life

The ocean could not do any of the above

if it was not in constant motion.

Let’s talk about Ocean Currents!

Have you ever felt the effects of an ocean current before? Have you ever been caught in a water current in a river or stream? What did it feel like?

What is an ocean current?

A large amount of ocean water that moves in a particular and unchanging direction

Ocean currents transport: dissolved minerals, solar energy, oxygen, carbon dioxide, fish,plankton (microscopic plants and animals which are an essential food source for many oceanic species)

There are 2 MAIN TYPES of ocean currents

1. Surface Currents

- caused by wind action, the earth’s spin and the

shape of the continents

-extend to a depth of 200 m

Wind Action

What causes the wind?

-Masses of air moving rapidly from one area to another because of temperature differences

-As air near the surface of the earth heats up it rises. Cooler air from higher in the atmosphere must then take its place. This air movement is what we call wind.

How does it affect currents?

-As air moves over the ocean it’s energy is transferred to water molecules on the surface which causesthem to move

What does energy transfer mean?

Here’s a little story to help you understand:

You (your name is Wind) are rollerblading along a level pathway. Your friend (Ocean) is up ahead also on rollerblades but is perfectly still facing away from you. Because you are Wind you like to sneak up on people so you rollerblade as quickly as you can with your arms straight out towards your friendOcean. Ocean is completely taken by surprise as you run into her (your hands slamming into her back and grabbing her). What happens to Ocean assuming that she doesn’t have a heart attack and fall over and that her rollerblades are lined up in the right direction? Right! Some of the energy that you have from rollerblading towards her is transferred to her body and you and her continue on down the path together! If you let go of Ocean she would continue on in the same direction even if she didn’t start trying to move on her own.

Therefore, the DIRECTION of the surface current is dependant on the WIND!

(Ocean’s direction would depend in the direction

in which you slammed into her!)

The Earth’s Spin (Good place for big earth ball)

-The earth rotates from west to east (that’s why the sun rises in the east and sets in the west!)

-Because of this rotation, in the northern hemisphere all currents flow clockwise and in the southern hemisphere all currents flow counter clockwise

-Known as the Coriolis effect

Continental Pebbles

  • Continents act similar to big rocks in a stream, deflecting the path of the current

Ocean currents of the world are shown in the diagram below. Do you see any major trends?

2. Deep Water Currents(Density Currents)

-caused by changes in density because of changes in temperature and salinity

-Deeper than 200 m

At the poles

  • water is colder and more dense so it starts falling towards the equator.
  • water starts to freeze leaving the salt behind which makes it even more dense and more sinkier

500 to 2000 years to complete the cycle

Notes and Activities – Science 8