Teaching Climate Change with Ice Cores

At the end of every school year we end our life science curriculum with geologic time. It's one of my favorite units because I get to bust out my fossil collection (If you know me, that's a big deal).
It's hard to talk about geologic time, mass extinctions, and evolution of species without bringing up climate change. All these topics are fascinating but there aren't a ton of hands on labs you can do with them. I decided to try something different this year and make my own ice cores for students to analyze. Most students had never heard of ice cores, and when I asked them how we learn about shifts in climate I got a lot of blank stares. It was a great opportunity to bring up a new topic.

Some background on ice cores:

• The best ice cores are taken from places where the snow doesn't melt. Over the years the snow layers on top of each other, compacts, and freezes into thick layers of ice. 
• ​Ice cores are generally drilled from Antarctica and Greenland. The oldest ice cores date back to 800,000 years ago. 
  
• Ice core layers are similar to tree rings- new layers form on top of the last each year.
  
• When analyzing the layers, winter snow layers appear lighter than summer snow layers. This is because the snow melts slightly in the summer, refreezes, and is more dense than the winter layer. When we count years in an ice core, a light band and a dark band make up 1 year of snowfall (see image below).
• As snow falls, particles from the atmosphere get trapped in the snow. We can use this ash, pollen, and even radioactive atoms to make inferences about what occurred during that year. 
• Air bubbles are trapped in ice core layers. Scientists can melt small layers of ice cores, trap the gas that is released, and measure the gas components to infer what the climate was like the past 800,000 years. Higher levels of greenhouse gases such as carbon dioxide and methane mean the climate was warmer.  
  

Materials you will need: 

• 8 pringles cans (or however many lab groups you want)
• Water
• Food coloring
• Ash (you can take some from your fireplace, or if you don't have a fireplace burn a sheet of paper from your recycling bin and collect the ashes)
• Rulers
• 8 Plastic tupperware containers from the dollar store
• Optional: plastic bugs from the dollar store
• Optional: carbonated water

Procedures:

1. ​Fill a large beaker with water. Fill a second large beaker with water and add a few drops of blue or green food coloring. Place both in the fridge until the water is chilled. 
2. Pour clear water into the bottom of each pringles can about 2 cm thick. This represents winter snowfall. Place in the freezer and allow to freeze solid. 
3. Once the first layer is frozen, pour a layer of colored water about 1 cm thick. This represents summer snowfall. Place in the freezer and allow to freeze solid. 
   
4. Keep pouring alternating layers. Feel free to pour some layers thicker than others to represent a high snowfall year. 
5. To have a layer that represents a volcanic eruption, add ash to the water before freezing.
6. Optional: If you would like to have bubbles in your layers, try using carbonated water instead of tap water. 
7. Optional: If you would like to add bugs, buy some small plastic insects from the dollar store and allow them to freeze in a layer. 
8. Once you have as many layers as you are aiming for (I wanted 12 layers representing 6 years) they are ready to go! The morning of the lab, peel the pringles cans away from the ice core and place the ice in a plastic container (see note below on why plastic is ideal). 
9. Give each group an ice core and a ruler so they can measure the layers and draw them to scale on their lab paper. I had them make inferences about each layer- was it a high snowfall year or low? What does the ash represent? What would bubbles represent? etc. 

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Some troubleshooting tips:

• When making ice cores, stick with water. The first time I tried making ice cores I used different liquids like sprite (for the carbonation) and instant coffee (to represent dust settling from the atmosphere) and it didn't work out well. These liquids have different freezing points than water and the ice cores did not hold up nearly as long. 
• If you pour your layers with already chilled water, they will freeze faster. I was able to get 3 layers poured per day: one layer before school, another layer at lunch, and a third layer before I went home for the day. I was aiming for 12 layers total, so it took 4 days of prep. 
• The first time I did this lab, I placed some of the ice cores in metal disposable containers from the dollar store, and a few in plastic tupperware containers. I noticed the ice cores melted MUCH slower in the plastic containers than the metal (afterwards I thought "duh... plastic is a better insulator"). If you need the ice cores to last all day, try using plastic. 
  
• Keep the ice cores in the freezer as much as possible. For the first half of class, I kept them in the freezer while we went through a powerpoint and discussed what ice cores are and what we can learn from them. I gave students about 20 minutes to analyze their ice cores, make their drawings, form inferences, and then they went right back into the freezer for the next class. If you do this, they should last you all day. 
  
• Since the ice cores melt and slide around a little bit, I stuck some masking tape on the tupperware ends and labeled the containers 'TOP' and 'BOTTOM' and then turned the ice cores on their side. That way when you get them in and out of the freezer between classes you won't get confused on which side is the most recent layer. ​
  

Overall the students enjoyed looking at their simulated ice cores and I was glad I got to throw in an extra lab during our geologic time unit. If you are interested in checking out the powerpoint and lab worksheet I used for this lesson, click here. If you would like to look at additional ice core information and dig through real data, check out this site. Have fun!

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