LESSON 4:

OCEAN CURRENTS

INTRODUCTION

There is a clear connection between ocean 

currents and climate. Ocean currents help 

to move heat, support rainforests on land, 

and make life possible for animals across 

the globe. Without ocean currents large 

parts of Earth would be unlivable. Humans 

are already seeing the impact of climate 

change on life in the sea. 

LESSON SUMMARY

This lesson helps students explore the 

role of the ocean in climate. They do this 

through an investigation to show how 

hot and cold temperatures help to move 

water around the world. Students examine 

temperature and precipitation data from 

two cities and use their understanding 

of water movement to explain why these 

cities have differences between their 

temperatures and rainfall. 

37

OBJECTIVES

• Students will use a demonstration as a 

model to explain how water moves in 

the ocean. 

• Students will analyze data about rainfall 

and temperatures in two cities in the 

world. 

• Students will describe how water 

movement and proximity to the ocean 

affect the climate in a location. 

ESTIMATED TIME

60 minutes. If you would like to divide 

this lesson among multiple days, good 

break points are between steps 4 and 5 or 

between steps 7 and 8. 
38

STANDARDS ADDRESSED

Science (NGSS): 3-LS4-3. Construct an 

argument with evidence that in a particular 

habitat some organisms can survive well, 

some survive less well, and some cannot 

survive at all.

3-LS4-4. Make a claim about the merit of 

a solution to a problem caused when the 

environment changes and the types of 

plants and animals that live there may 

change.

3-ESS2-1. Represent data in tables and 

graphical displays to describe typical 

weather conditions expected during a 

particular season.

3-ESS2-2. Obtain and combine information 

to describe climates in different regions of 

the world.

OCEAN LITERACY 

PRINCIPLES

1a The ocean is the defining physical 

feature on our planet Earth.

1c Throughout the ocean there is one 

interconnected circulation system.

FOCUS QUESTION

How do currents in the ocean affect 

weather and climate on land? 

MATERIALS

• Ice water

• Hot water, heated in an electric kettle, 

on a hot plate, or from a coffee machine

• Clear or transparent container (glass or 

heat resistant). A deeper container will 

help students observe the results more 

easily; however, a dish such as an 8” x 

8” baking dish will work if that is what is 

available.

• Two distinct colors of food coloring, 

such as red and blue

• World Map master, one for display

• Milwaukee and Hobart Climate Data, 

one per student

• Oceans and Climate, one per student

PREPARATION

• Read Lesson 2 in this guide. Consider 

if completing that lesson with your 

students might help support their 

learning in this lesson. 
39

• Practice the demonstration, as 

described in step 3 below, to ensure 

that your set up works well. Adding hot 

water to the dish then slowly adding ice 

cold water to one side is one effective 

set up, though other variations such as 

adding ice to one side and letting it sit 

for several minutes may also work well. 

• Decide how many times you want to 

repeat the demonstration to ensure 

that all students can easily make 

observations. Ensure you have enough 

materials prepared to repeat the 

experience a few times.

FACILITATION

Step 1. Share with students that the ocean 

is very large. We cannot simply stand on a 

beach and see how the water moves. Today 

they are going to have a chance to explore 

how one kind of current in the ocean 

moves water. 

Step 2. Set up the demonstration in a way 

that students can see what happens in the 

dish from the side. To set it up, complete 

the following steps.

• Place the transparent container on a flat 

surface. Add hot water to the dish to fill 

it at least halfway.

• Add ice or ice water to one side of the 

dish. Do this very carefully to minimize 

mixing the hot and cold water. If you 

are adding ice water, try adding it very 

slowly along one side of the dish so 

that it does not disturb the water on the 

other side of the dish.

• With students watching carefully, add 

3 drops of red food coloring (or another 

color) to the hot side of the dish, about 

an inch from the side. Add 3 drops of 

blue food coloring (or another color) 

to the cold side of the dish, about an 

inch from the side. Ask students to 

observe what happens over the next 3 

minutes. You may wish to point out key 

observations, listed below, if students 

do not seem to be noticing them.

Observations: Students should be able 

to see that the food coloring on the cold 

side sinks to the bottom and then begins 

traveling toward the hot side of the dish, 

along the bottom. The food coloring on 

the hot side will disperse more quickly but 

should generally move toward the cold side 

of the dish. 
Step 3. Ask students about why they 

think the colors moved the way they did. 

They do not have to develop a complete 

understanding but should know that the 

heat and water from the warm side moves 

to the cold side. As it cools off, it sinks and 

pushes water that is already on the cool 

side out of the way, toward the warm side. 

That water warms up, rises to the top part 

of the water in the dish, and the process 

creates a current. Draw a representation on 

the board as you discuss these ideas

Step 4. Explain that there are other kinds of 

currents in the world, including some that 

move by wind, tides, and the way the Earth 

rotates. Share with students that large 

currents depend on both heat and salt, but 

for now they are going to focus on heat. To 

relate this to ocean currents, show students 

the World Map master and ask where 

temperatures are warm and where they are 

cold. Students are likely to know that it is 

hot near the Equator and cold at the north 

and south poles. Ask them to connect what 

they saw in the demonstration to the water 

on Earth. 

40
41

Step 5. Point out the two cities that 

are shown on the World Map master—

Milwaukee, WI and Hobart, Australia. Share 

with students that Hobart, the capital of 

Tasmania, is at 43 degrees latitude south. 

Tell them that in the United States, the city 

of Milwaukee, Wisconsin is at 43 degrees 

latitude north, so they are the same 

distance from the equator. Ask students the 

following questions and accept all ideas at 

this point.

• How would you describe where each 

city is and what is around it? 

• Do you think that the temperatures in 

Hobart and Milwaukee are the same or 

different? Why?

• Do you think the amount of rainfall in 

Hobart and Milwaukee is the same or 

different? Why? 

Step 6. Share with students that they 

are going to have a chance to learn 

more about temperatures and rainfall in 

the two cities. Distribute the handout, 

Milwaukee and Hobart Climate Data, to 

students. Ask them to graph the data using 

a strategy appropriate for your students. 

The following are suggestions for how you 

might have students analyze the data. 

• As a class, create a bar graph to show 

the average temperatures in each 

location and another to show the 

average rainfall in each location. If your 

students are not comfortable graphing 

on their own, this is the best option.

• Have pairs of students graph 1 of the 

4 sets of data (rainfall in Milwaukee, 

rainfall in Hobart, precipitation in 

Milwaukee, precipitation in Hobart), 

then compare the two rainfall graphs 

and the two temperature graphs.

• Have small groups of students create 

two bar graphs on one set of axes to 

compare either the rainfall in both 

places or the temperatures in both 

places. This could also be divided by 

season and have students add their 

graphs to a common class graph.
42

Step 7. Lead a class discussion to compare 

the rainfall and temperatures in both cities. 

Students should see that in Hobart, both 

temperatures and precipitation are more 

even through the year, creating a mild 

climate. Milwaukee has a more distinct 

variation in temperature and amount of 

rainfall across the year. Ask students if they 

have any ideas of why that might be but 

accept all answers at this point. 

Step 8. Tell students that they are going to 

have a chance to create a comic to learn 

more about why the two places might be 

different. Distribute the Ocean and Climate 

handout and different-colored pens or 

pencils. Show students that there are five 

boxes that will make up the comic and each 

has a description, with the fifth box being 

a summary of the other boxes together. 

Tell them that their task is to draw pictures 

for each box to show what the words are 

describing. They can discuss their ideas in 

their small groups to make sure everyone 

understands but emphasize that each 

student should draw pictures on the comic 

individually. Tell students that the goal is 

to be able to explain how the ocean affects 

climate, particularly when they think of 

Milwaukee and Hobart. 

Step 9. Lead a class discussion to talk 

about their comics. Make sure they link box 

4 of the comic to the demonstration. 

Have them discuss how the story in the 

comic relates to temperature and rainfall 

in Milwaukee and Hobart. As part of the 

discussion, share the Ocean Currents 

animation from Science on a Sphere 

(https://sos.noaa.gov/catalog/datasets/

ocean-circulation-labeled-currents/). You 

may wish to point out:

• that the animation distinguishes 

between warm surface waters (red 

arrows) and deep, cold waters (blue 

arrows), 

• gyres, which are the currents that 

are affected by heat and salt like the 

demonstration, 

• other types of currents, such as the 

equatorial currents,

• that currents move water long distances 

around the world, and

• that Hobart is on an island south of 

Australia with a warm current running 

near it while Milwaukee is far inland and 

is less affected by ocean currents.

After the discussion, encourage them to 

explain why Milwaukee has more variable 

weather than Hobart, using their comic as 

a reference. They should relate it to both 

warm currents and to evaporation of water 

leading to storms. 
Step 10. Remind students of the 

demonstration. Ask, what would happen 

if the two sides of the dish had water that 

was a similar temperature? How would 

that affect the story in their comics? If 

they struggle to reason through what 

would happen, consider repeating the 

investigation with one temperature of 

water while still using two colors of food 

coloring at opposite ends. Students should 

see that the food coloring disperses the 

same way on both ends and does not travel 

toward the other side of the dish. 

Step 11. Ask students to use the discussion 

from the previous step with their comics to 

explain how Hobart would be different if 

the water at the poles became too warm for 

sea ice to form. 

Milwaukee, 

Wisconsin, 

USA

43° North

Average High 

Temperature 

(°F)

Rainfall 

(inches)

Hobart, 

Tasmania, 

Australia 43 ° 

South

Average High 

Temperature 

(°F)

Rainfall 

(inches)

January 31 1.79 January 69 2

February 34 1.69 February 68 1.9

March 44 2.20 March 65 1.9

April 55 3.86 April 60 2

May 67 3.54 May 55 1.9

June 77 4.38 June 51 1.9

July 82 3.40 July 50 2.2

August 80 3.65 August 52 2.5

September 74 3.16 September 55 2.4

October 61 2.78 October 59 2.4

November 48 2.24 November 62 2.6

December 36 1.88 December 66 2.6

43
44

EXTENSION

Divide students and have half the class learn about the plants and animals that live in Tasmania 

while the other half learns about plants and animals that live in the Milwaukee area. Have them 

choose one plant or and learn more about its life, including what might happen to the plant or 

animal if the climate in its home area changed. Have students share what they learned with the 

class so that they hear about plants and animals in both areas, then hold a class discussion about 

what would happen to living things if the climate changes where they live. 

Lesson 4 NOAA Reference

• Science on a Sphere Ocean Circulation (https://sos.noaa.gov/catalog/datasets/oceancirculation-labeled-currents/)
WORLD MAP

45
46

THE OCEAN AND CLIMATE

1

2

3

The ocean absorbs energy from the sun, especially near the equator. This 

makes the ocean warmer, and it stores the heat. 

When the water heats up some of it will evaporate into the air. This warms 

up the air. It also makes it more humid, or moist. 

The extra heat and humidity cause rainstorms. These storms move long 

distances because of winds. The rain often falls on land. 
47

THE OCEAN AND CLIMATE

4

5

Heat also moves with ocean currents. Some currents are part of cycles that 

start with sea ice in the poles. Other currents move because of wind, tides, 

or the way Earth rotates.

Summary: Heat and water move around Earth both in the ocean and in the 

air.