Who are you?
I’m Tas Van Ommen. I work for the Australian Antarctic Division and I lead the Ice Cores Project there.
What is an Ice Core?
Ice cores are valuable sources of past climate information. They’re basically cylinders of ice that we drill out of the Antarctic ice sheet. They contain information on the climate that gets deposited with the layers of snow that fall on the continent year by year. These layers carry with them all sorts of information about the atmosphere and its contaminants over time.
By analysing ice cores, we learn a great deal about the processes that control the climate. We learn how it’s changed in the past and how ice ages have come and gone.
What do Ice cores tell us about past atmospheres?
One of the most valuable indicators we get from ice cores comes in the form of tiny bubbles of past atmosphere that get trapped between the snow flakes as the ice builds up on the continent. We can bring the ice cores back to the laboratory, crack open the bubbles which are like tiny time capsules of past atmosphere and analyse them to determine past levels of greenhouse gases. What we find is really startling. The carbon dioxide levels over the past 800,000 years track the temperature record incredibly closely, showing that there is a tight link between CO2 and climate.
How do we date Ice cores?
If you look at an ice core you can not visibly see the layers of annual snow. However, in almost all of the measurements we make, you can actually detect and count these layers to date the ice core in much the same way that you can count tree rings.