Paleoclimatologists study ice cores to investigate earth’s past climate. they use methods such as oxygen isotope analysis. which feature inside the ice are the scientists interested in analyzing and why?

The scientists are interested in bubbles of atmosphere trapped in the ice cores. By the depth of the ice, they have some idea of the age of the atmospheric bubbles. By the composition of gasses in the trapped air, they can determine the proportions of atmosphere made from the composite gasses: nitrogen, oxygen and carbon dioxide and a few other gasses. This is how scientists have determined that the proportion of carbon dioxide has increased in our atmosphere since the Industrial Revolution.