Final answer:
Antarctic ice cores are primarily used for paleoclimatic reconstructions, providing climate proxies that help scientists estimate past Earth temperatures and atmospheric CO₂ concentrations.
Step-by-step explanation:
Most ice cores used in paleoclimatic reconstructions come from Antarctica. The collection and analysis of Antarctic ice cores have made it possible for scientists to estimate the temperature of the Earth over the past 400,000 years. These cores contain air bubbles and other biological substances that act as climate proxies, providing insight into past atmospheric CO₂ concentrations and temperature cycles. Antarctic ice cores have revealed periodic cycles of warming and cooling, which are crucial to understanding Earth's climate history.
Drills are used to retrieve ice cores from deep within the polar ice sheets and high mountain glaciers, reaching depths of thousands of meters. As scientists delve deeper into the ice, they are able to travel back in time, with the deepest layers representing the earliest time periods. By studying the air bubbles and biological evidence trapped in the ice, such as the isotopic composition of water molecules like deuterium, researchers can infer past climate conditions, including temperatures relative to modern day.