Water, snow and ice

In this learning sequence, students investigate water cycles in Antarctica and discover the different types of ice found in Antarctica and how it forms. They conduct experiments to investigate ‘density and salinity’ and ‘temperature and density’ and discuss how these factors influence ocean movements. Students find out how scientists undertake research to gather data about changes to ice in Antarctica. They create their own interview with a science character to show what they’ve learned about changes to ice in Antarctica.

Setting the scene

Water cycle in Antarctica

Discuss what the water cycle is and how it relates to where students live. Discuss where rain comes from and the effect of the sun on water bodies such as oceans, lakes and rivers. What happens to rain as it falls to the ground? Refer to a diagram of the water cycle.

Pose the question: Is the water cycle different in Antarctica? Ask students to draw a scientific diagram of the water cycle in Antarctica. How might the climate and water cycle influence each other? In what forms would water exist in Antarctica?

How cold is Antarctica?

Use a video as a discussion starter about what happens to water in the Antarctic. The video on this web page shows what will happen to boiling water when thrown into the air (−28°C). Prior to watching ask students to predict what may happen to the water.

  • Describe the students’ observations: The boiling water evaporates and then forms a mist of ice crystals (which are super-cooled water droplets)
  • Develop an explanation: The boiling water turns to ice due to the extremely cold, dry Antarctic air and the increased surface area of the boiling water.

In cooperative groups, list all the forms of water and variations of ice that are found in Antarctica. To prompt discussion, ask:

  • Where does the water come from?
  • How does the ice on Antarctica get thicker?
  • Where do icebergs come from?
  • What happens when snow falls in the ocean?
  • What happens to ice in summer?

Ask students to sort and classify each of the forms of water as freshwater or seawater. Use this task to assess students’ prior knowledge.

Explore and research

Ice in Antarctica

Terms such as pack ice, ice sheet and ice shelf may have come up in discussion. Discuss the fact that there are different forms of ice across Antarctica. Guide students’ research of these ice types to find out differences and how each is formed. Provide students with a copy of the Forms of ice in Antarctica worksheet [PDF].

Provide access to the information on:

Ask students to create a visual representation of the types of ice in Antarctica that highlights their differences.

Freshwater and seawater density

Discuss what happens when a glacier melts. What happens to the freshwater as it flows into the sea?

Conduct an investigation to show the different density of seawater compared to freshwater. In this investigation:

  • Fill three small containers with water, with a different colour food dye added to each.
  • In one container have only freshwater; the next add 1 teaspoon of salt and the last add 2 teaspoons of salt.
  • Use a clear straw as a pipette. Place the straw in the first container and a thumb over the straw. As you draw the straw up a small amount of coloured water will be in the straw. Now place the straw in the next container. Remove your thumb and replace it. As you draw out the straw you should see two coloured layers of water. Repeat the process in the next container.
  • You should see three distinct layers of coloured water in the straw.

Discuss students’ observations and ask them to explain why there are three distinct layers. Refer to the density of water and from this experiment identify which is less dense; sea water or freshwater. Encourage students to use the term salinity when discussing the amount of dissolved salt in the water. The container with 2 teaspoons of salt has higher percentage salinity and is higher in density than both the freshwater and the water containing only 1 teaspoon of salt.

Follow up the density investigation with another investigation following the format ‘predict, observe and explain’.

Add warm water to a large, clear glass bowl. In a jug chill water and add food colouring.

  • Predict what will happen when the chilled, coloured water is carefully and gently poured into the clear glass bowl of warm water.
  • Observe that the coloured water sinks and forms a layer with the clear warmer water above.
  • Explain your observations.

Relate the density of freshwater and seawater to what happens in Antarctic oceans. Discuss the other variable which is water temperature. How do these two variables influence ocean circulation?

Freezing: freshwater and saltwater

Investigate the freezing rates of seawater and freshwater.

Make ‘seawater’ by completely dissolving 25 g of salt in 250 mL of warm water and letting it cool to room temperature. Then fill two polystyrene cups: one with 250 mL of freshwater and the other with 250 mL of saltwater. Add blue food dye to each to help show what happens to the salt after freezing. Place a mark to indicate the water levels.

Label the containers and place them inside a freezer. If possible examine the cups after an hour, then every 10 minutes, until there is a thick crust of ice on the top. The class could then discuss any differences in how quickly each liquid became frozen.

After 24 hours in the freezer, remove each from the polystyrene cup and examine the ice. Observe what happened to the salt. Use a hand lens to view the crystals. Using safety glasses, carefully place both types of ice on a cement mat and carefully tap them with a hammer to test their hardness. Which ice is the hardest? Why should this be the case?

Explain and share

Seasonal sea ice changes

Ask students to consider how sea ice around Antarctica might change during the year.

Sea ice reflects sunlight causing a significant amount to be reflected into space. In summer more of the ocean is exposed to the sun’s rays. The darker ocean absorbs the sunlight and the ocean warms. Why is sea ice important to maintaining the Antarctic climate and environment?

Satellite imagery provides a view of the changing area of sea ice. Investigate the changes by looking at monthly sea-ice extent images for Antarctica. Describe reasons for the sea ice changes that occur from year to year. Why is it important to keep a record of these seasonal changes over numbers of years?

Scientists also need to know the sea ice thickness.

View the video on this page, about Mapping East Antarctic sea ice.

Through the video, pause and discuss these points:

  • Scientists are measuring sea ice thickness. Why is that important?
  • How are scientists able to make a 3D map of the sea ice floe?
  • Why is it important for scientists to measure changes in sea ice over time?
  • How is the helicopter equipped to collect sea ice data?

What are the implications of a shrinking and thinning sea ice?

Ice sheets and sea level rise

Review the difference between the Antarctic ice sheet and sea ice.

Conduct a straw poll to survey what students believe to be the percentage of the world’s ice that is locked up in the Antarctic ice sheet. It may surprise students that ninety per cent of the world’s ice (29 million cubic kilometres) and approximately 80 per cent of its fresh water, is locked up in the Antarctic ice sheet.

What would be the impact if the Antarctic ice sheet shrinks due to climate change?

Guide student discussion and refer to background information: Ice sheets and sea-level rise.

Elaborate and apply

Ice cores and climate change

Ask students why scientists study ice cores drilled from the ice in Antarctica. Explain how bubbles of air trapped in the ice are a record of the atmosphere over time.

View video of scientific studies into ice cores.

Glaciers: calving and retreat

How large are glaciers in Antarctica? Provide students with a reference, for example the Lambert Glacier, the world’s largest glacier, is about 40 km wide and 400 km long.

Discuss the calving (the breaking of the end of a glacier).

View the videos on these pages about glaciers:

Points to discuss after viewing include:

  • What communities were found living under the glacier tongue?
  • Discuss the effect of warm ocean water on the floating glacier.

Ice shelf

Review the different types of ice in Antarctica including an ice shelf.

Ask students to research the events that lead to the collapse of The Larsen B Ice Shelf.

What was unusual about the summer temperatures in that year and in previous years? How might this have contributed to the collapse of the ice shelf? Why wouldn’t the collapse of an ice shelf contribute to sea level rise?

Discover what happened to the Wilkins Ice Shelf in 2008.

View a series of satellite images of the Larsen B Ice Shelf collapse in 2002.

Evaluate

Why study ice in Antarctica?

Create a short interview portraying a scientist who is studying changes to the ice in Antarctica. Work in collaborative groups to develop questions to be answered by the scientist. Encourage students to incorporate ideas about climate change.

In their groups, students:

  • choose a field of study e.g: glaciers, ice sheets, sea ice, ocean and climate
  • develop a scientist character
  • develop questions and answers
  • film or present the interview.

Review students’ initial ideas about the water cycle and add any new information. What ideas have changed as a result of their inquiry? What new ideas have they learned?

Assessment ideas

At various points in the learning, assess to what extent students:

  • describe the flow and cycle of water in Antarctica
  • describe the different forms of ice in Antarctica
  • describe relationship between ‘salinity and density’ and ‘temperature and density’
  • describe ways in which scientists study changes to ice in Antarctica, particularly in relation to climate change.