Some of these cylindrical ice cores—each about the width of a pool noodle—hadn’t seen daylight for 100,000 years. They’re clear and flawless, “like window glass,” says Jørgen Peder Steffensen, a glaciologist at the Niels Bohr Institute in Copenhagen, Denmark, who, along with glaciologist Dorthe Dahl-Jensen, oversaw the camp’s daily operations. Researchers working in the Arctic and Antarctica have come to realize that this ice provides a rare view of the past, one that’s disappearing rapidly as climate change speeds melting at the poles.