In this lesson students model how scientists use data from ice to make inferences about what the climate was like thousands of years ago.
You start with a short introduction to ice cores and ice core data before moving on to a hands-on activity where students create a model ice core based on given climate scenario.
Essential questions to consider:
How does layering show change over time? What observations can we make about different materials that form layers? How can we compare layers to understand time sequences?
How does ice form layers? What are the properties of ice layers that hold clues to the history of climate change?
Background Information Required:
Snow is basically ice crystals which have formed from frozen water vapor in clouds. On the ground, these ice crystals are loosely packed with one another, with air pockets between the ice crystals. The structure of ice allows mixing with other substances. Gases flow through, and get trapped. Ice therefore tends to preserve the history of its formation. The middle of Antarctica and Greenland very rarely experience any melting, and so the snow continues to pile up. In the winter, more snow and finer snow falls. In the summer, the warm temperatures create layers of snow with larger crystals. These layers continue to be visible at depth, with thicker, finer winter layers and thinner, coarser summer layers alternating on top of the other. At about 100 m depth, the snow becomes compressed into ice from the weight of the snow layers above it. The air space between the snow crystals become squeezed out, so that small, isolated air bubbles are left.
Just as tree rings are clues that tell the story of climatic conditions over time, so layers of ice can hold clues to global climate changes. Scientists can use annual snow layers, volcanic dust layers, and fallout from nuclear bomb tests as markers of time in the ice cores. Scientists can analyze gases, dust particles, and other particles that are trapped to model the climatic conditions that explain what they find. Ice layers on Earth preserve the history of global climate change. The bottom of the ice sheet in Greenland is two miles below the surface. That is equal to 100,000 years of ice.
Credit: Jo Dodd email@example.com
Cost: $35.00 - $45.00 per classroom*
*An alternative option is to make your own colored dough. You will want to make 5x the amount listed below for your class. Here is the recipe:
Colored "Faux" Dough
Mix everything but the food coloring together in a large pot until somewhat smooth. It will be lumpy. Not to worry, the dough will get smoother as it cooks. Cook the dough over a low heat. Mix frequently. The water will slowly cook out of the mixture and you'll notice it starts to take on a sticky dough appearance. Keep mixing until the edges of the dough along the side and bottom of the pan appear dry. Pinch a piece of dough. If it’s not gooey, the dough is ready.
Place the dough on a counter top or large cutting board that can withstand a little food coloring. Knead the warm dough until it’s smooth and then divide it into the number of colors that you’d like to make. I divided mine into four balls, flattened each of them, added a little bit of food coloring, and then kneaded it in. I added more food coloring to get the desired shades
NOTE: The cream of tartar makes this dough last 6 months or longer, so resist the temptation to omit this ingredient if you don't have it on hand. Store this dough in an airtight container or a Ziploc freezer bag.
Some scientists collect data from tens of thousands of years ago. How do you think scientists can know what happened so far in the past? Turn and talk with a neighbor.
Give time for students to talk. While they are talking, I get prepared to show the Ice Core Slides. Bring the class back together then elicit a few responses from the class.
Bring up the Ice Core Slides (How do We Know).
Show students slide #2, pointing out that the data goes back 100,000 years.
Ask for student input about how data is collected, especially from periods long ago. (Talk about thermometers, satellites, etc. and introduce ice cores if students don't suggest this.)
Note: If you have access to streaming video, you may replace the slide show and data analysis with the KQED video (20 minutes) on ice cores. It provides a nice context to the usefulness of using ice cores to study climate change.
Web Quest: At the Core of Climate Change
Extreme Ice: National Ice Core Lab
Set up trays for each table group that includes a bit of each of the materials.
Working in groups of three to four, students will create layers of snow and ice represented by the different colors of play dough.
Occasionally, stop them for a global event, such as a volcanic eruption. They will add something else to their layers to represent this event. One member of each group needs to be a timekeeper, recording the beginning time, global event times, and ending time. After the layering has stopped, groups will exchange their ice layers and extract a core sample to analyze.
Tips for managing this activity.
1) Establish who will act as time keepers. Make sure they have stopwatches and a place to record the time and the event.
2) This is not a race, so establish a nice pace at the start.
3) Having students pre roll out larger and smaller pieces for winter and summer does help with time management.
Narrative: This could be done with different global events that each group draws randomly…or each group has several specific events for 100 or l000 years of time, such as pollution in the air after the Industrial Revolution began, radioactive fallout from nuclear events including tests, major volcanic eruptions. This version has each group constructing their layers with the same global events.
Working in groups of three to four, you will create layers of snow and ice represented by the different colors of play dough. Occasionally, I will stop you for a global event, such as a volcanic eruption. You will add something else to your layers to represent this event. One member of the group needs to be a timekeeper, recording the beginning time, global event times, and our ending time. You will need to use a stopwatch to track the time passed in seconds. After our layering has stopped, groups will exchange their ice layers and extract a core sample to analyze.
* Someone in each group should be a time keeper. Note the beginning time, major events, and ending time.
“It is winter and most of the year’s snow is falling and accumulating. Use a small handful of blue dough to create the winter snow fall. Roll out a ping pong ball size of snow. Press this down into the clear cup.
During the summer there isn't as much snow ... a few centimeters accumulates. Use the green dough to represent the summer snowfall. Roll out a piece of a size large marble. Press this down into the cup making a layer on top of the first.
Continue layering winter and summer snow.
* STOP with whatever layer you are adding. Record the time. There is a volcanic eruption. It is a major volcanic event, sending ash high into the atmosphere. Use your black colored sand to layer ash over the last snow layer. Make sure you sprinkle it over the surface. You may want to blow gently so that the ‘ash’ is not distributed evenly.
Continue your seasonal layers of snow.
* STOP layering, record the time. There is more volcanic ash falling. In fact, it is falling for several weeks. Add more black sand to your last snow layer.
Continue your seasonal layers of snow.
*STOP layering. There are acids in the snow from industrial pollution. Nitric acid and sulfuric acid is falling with the snow. Add yellow sand to your last snow layer.
Continue your seasonal layers of snow.
*STOP layering. Record the time. There is fallout in the atmosphere from above ground atomic testing. Add the salt so that it covers the last layer.
Continue to add one more year of snow. STOP. Record the time.
Analyze ice layers using ice cores:
Exchange your layers with an adjacent team. Extract an ice core sample for the thickness of the layers using the plastic tube. Leave the core sample in the plastic tube. Use the data sheet on the next page to:
In the video below two of my students reflect on how using this model helped them to connect climate science.
Guide the class through a discussion asking them explain their analysis of the ice cores.
Here are an additional set of discussion questions with answers:
Q: How many years were you able to sample from your core? How can you tell?
A: Answers will vary. I can count the number of years because I know that the thick blue layer is winter and the thinner green layer is summer and together they can be considered one year.
Q: What conditions must a location have in order for ice cores to be useful?
A: For ice cores to be useful, they must be taken from a very cold location where the snow never melts such as Antarctica or Greenland.
Q: How do you think scientists determine historical temperatures using ice cores?
A: Scientists use the thickness of the ice layers to determine temperature. For example, they can determine the difference between winter and summer and they can determine the difference between a warm period and an ice age.
Q: How do you think scientists determine the amount of CO2 in the atmosphere using ice cores?
A: Since snow where ice cores are taken never melts, new snow is continually being layered on top of old snow. Eventually, the pressure from the weight of the snow causes the older snow to become very compact and traps any air between the snowflakes into tiny bubbles. Scientists can analyze the composition of the air bubbles and find out what percentage of their sample consists of CO2.
Q: How is the amount of carbon dioxide represented in your model? How is your model different from real ice cores? Use your ice core and make one observation about the amount of carbon dioxide in your ice core sample.
A: The amount of carbon dioxide is represented in the model by using yellow sand in between each layer. The amount of sand is directly correlated to the amount of carbon dioxide in the atmosphere during that time period. My model is different from a real ice core because real ice cores have CO2 trapped in air bubbles throughout the entire sample, while my model has the amount of CO2 represented between each layer.
Q: Do you think scientists can use real ice cores to make accurate predictions about weather events hundreds of years ago? Why or why not?
A: Yes, scientists can extrapolate a great deal of information from ice cores including, temperature, length of seasons, levels of atmospheric gases, and volcanic activity.
Q: Do you think ice cores look the same in different parts of the world? What do you think causes differences or why do you think they are the same?
A: Ice cores from different parts of the world do look slightly different due to variations in temperature and snowfall in different locations. Although different, ice core data consistently show the same pattern of warming and cooling throughout time.
As an extension to this activity you could send students to the Antarctic Glaciers website, to read the article Ice cores on the Antarctic Peninsula. I would ask them to create a set of Cornell notes from this reading. They look for main ideas, supporting details, word choice and also analyze any graphics and captions.
In addition, the Natural History Museum (London) has a great Ice Cores video (with supplemental reading) of a climatologist talking about the process of making and interpreting ice cores.