Ocean Currents Ocean Currents

Text Book Page # 380 - 385Text Book Page # 380 - 385

Warm-up discussionWarm-up discussion

Imagine that you are at the beach, and you Imagine that you are at the beach, and you get into the water and begin swimming. get into the water and begin swimming. Describe what happens if you stop Describe what happens if you stop swimming.swimming.

1.1. What does the water feel like?What does the water feel like?2.2. What does the water do to your body?What does the water do to your body?3.3. Do you stay in the same spot? If not what Do you stay in the same spot? If not what

happens?happens?

Discuss at table and elect one speaker to Discuss at table and elect one speaker to share out.share out.

CURRENTSCURRENTS

What is an ocean current?What is an ocean current?

A large stream of moving water A large stream of moving water that flows through the oceans.that flows through the oceans.

Currents are Important Currents are Important Because….Because….

- They help to move boats and shipsThey help to move boats and ships- They mix nutrients around the They mix nutrients around the

oceans oceans - They bring up small organisms and They bring up small organisms and

plants to the surface so that animals plants to the surface so that animals like birds can feed on them like birds can feed on them (upwelling and downwelling). (upwelling and downwelling).

- Effects climates (El Niño and La Niña)Effects climates (El Niño and La Niña)

Difference between Waves and Difference between Waves and Currents Currents

- Unlike waves, currents carry water Unlike waves, currents carry water from one place to another. from one place to another.

Two types of ocean currentsTwo types of ocean currents

Surface CurrentsSurface Currents Deep CurrentsDeep Currents

Surface CurrentsSurface Currents

Surface currents, which affect water to Surface currents, which affect water to a depth of several hundred meters, are a depth of several hundred meters, are driven MAINLY by winds.driven MAINLY by winds.

Surface currents are caused by Surface currents are caused by the followingthe following

1.1. WindsWinds

2.2. The Earth’s Rotation (Coriolis Effect)The Earth’s Rotation (Coriolis Effect)

3.3. Temperature differences in ocean Temperature differences in ocean waterwater

4.4. Continents (continental Deflection)Continents (continental Deflection)

2. The Coriolis Effect2. The Coriolis Effect

The Earth’s rotation causes wind and The Earth’s rotation causes wind and surface currents to move in curved paths surface currents to move in curved paths rather than in straight lines. Due to this:rather than in straight lines. Due to this:

- Currents in the 2 - Currents in the 2 hemispheres move in hemispheres move in different directions. different directions.

- Currents in the - Currents in the northern hemispherenorthern hemisphere move in a move in a clockwise clockwise directiondirection. .

(from 12- 6 o’clock, OR (from 12- 6 o’clock, OR from East to West) from East to West)

- Currents in the Currents in the southern hemispheresouthern hemisphere move in amove in a

counter clockwisecounter clockwise direction (like going direction (like going backwards on a clock backwards on a clock OR from West to East).OR from West to East).

3. Temperature Differences3. Temperature DifferencesThere are warm currents and cold currents.There are warm currents and cold currents.

- Warm water wants to moves from the equator to the Warm water wants to moves from the equator to the polespoles

- Cold water wants to move from the poles to the Cold water wants to move from the poles to the equatorequator

This creates a consistent movement of water. This creates a consistent movement of water.

- The cold water sinks to the bottom and moves towards The cold water sinks to the bottom and moves towards the equator WHILEthe equator WHILE

- The warm water floats and moves towards the poles. The warm water floats and moves towards the poles.

How does temperature affect How does temperature affect currents?currents?

Warm currents Warm currents - Some currents carry - Some currents carry warm water (eg. The Gulf Stream)warm water (eg. The Gulf Stream)

Cold currents Cold currents - Some currents carry cold - Some currents carry cold water (eg. The California Current)water (eg. The California Current)

Where do you think the warmest and Where do you think the warmest and coldest oceans on Earth are? (Discussion)coldest oceans on Earth are? (Discussion)

Warm currentsWarm currents start at start at the equatorthe equator

Cold currentsCold currents start at start at the north and south the north and south polespoles

Therefore Therefore warm warm currentscurrents flow from the flow from the equator to polesequator to poles

Cold currentsCold currents go from go from poles to equatorpoles to equator

Table DiscussionTable Discussion

Ocean GyresOcean Gyres

Ocean gyres are large system of circular ocean currents formed by global wind patterns and forces created by Earth’s rotation.

The five major circulation patterns formed by the currents on this map are the world's five major ocean gyres: North Atlantic, South Atlantic, Indian, North Pacific, and South Pacific. (The Indian Ocean Gyre is actually two, split slightly below the Equator.)

Ocean GyresOcean Gyres

Deep CurrentsDeep Currents

Stream like movements of ocean Stream like movements of ocean water far below the surface.water far below the surface.

Deep CurrentsDeep Currents Deep Cold Currents flow slowly.Deep Cold Currents flow slowly. Caused by differences in the density Caused by differences in the density

of ocean water.of ocean water.

1. Surface currents carry warm water toward the 1. Surface currents carry warm water toward the poles.poles.

2. As the water cools, ice forms. The colder, saltier 2. As the water cools, ice forms. The colder, saltier water is denser and sinks.water is denser and sinks.

3. Deep currents carry cold, dense water toward 3. Deep currents carry cold, dense water toward the equator.the equator.

4. As the water warms, it becomes less dense and 4. As the water warms, it becomes less dense and rises.rises.

Self - assessmentSelf - assessment1. What is a current?1. What is a current?

2. What are the 2 types of currents AND how are they 2. What are the 2 types of currents AND how are they different?different?

3. how do currents in the north hemisphere of the earth 3. how do currents in the north hemisphere of the earth differ from the movement of currents in the southern differ from the movement of currents in the southern hemisphere?hemisphere?

4. How do warm currents on earth move around the 4. How do warm currents on earth move around the earth?earth?

5. How do cold currents move around the earth?5. How do cold currents move around the earth?

6. Why do you think warm and cold currents move in the 6. Why do you think warm and cold currents move in the way that they do around the earth?way that they do around the earth?