A cylindrical sample of ice, typically from the ice sheets of Antarctica and Greenland or from mountain glaciers.
Ice cores are used by paleoclimatologists for determining ancient climate conditions.
Snow is formed by crystallization around small particles in the atmosphere, and these particles fall to the ground with the snow. The particles could be ash from erupting volcanoes, pollen, or smoke, and provide the scientists with clues about the environment and climate at the time the snow fell.
When the snow lands on the ice, air fills the space between the ice crystals. As more snow settles on top of it, the ice gets compressed and eventually tiny air bubbles get trapped in the ice. The bubbles contain the gases of the atmosphere at the time they became trapped in the ice. This information is also of great value for reconstructing past climate conditions.
In addition the ice itself reveals information. The relationship between heavy and light water molecules in the snow depends on the temperature at the time the snow fell. A low content of heavy water molecules indicate a cold climate, and a high content a warm. By analyzing the ice core it is possible to construct a vertical time line of temperatures going back many thousands years.
Ice core research has recently dated the end of the last ice age at exactly 11,711 years ago.
The different climatic information contained in ice cores make them an important tool for paleoclimatologists.