Through analysis of ice cores, scientists learn about glacial-interglacial cycles, changing atmospheric carbon dioxide levels, and climate stability over the last 10,000 years. This picture shows a traversing field camp from December 2010. From top to bottom: * Levels of carbon dioxide (CO2). High rates of snow accumulation provide excellent time resolution, and bubbles in the ice core preserve actual samples of the world’s ancient atmosphere.
Seasonal differences in the snow properties create layers – just like rings in trees.
Unfortunately, annual layers become harder to see deeper in the ice core.
It must have a suitable freezing point and viscosity.
Collecting the deepest ice cores (up to 3000 m) requires a (semi)permanent scientific camp and a long, multi-year campaign.
The bottom plot shows global ice volume derived from δ18O measurements on marine microfossils (benthic foraminifera) from a composite of globally distributed marine sediment cores. An example of using stable isotopes to reconstruct past air temperatures is a shallow ice core drilled in East Antarctica.