Reconstructing 800,000 years of greenhouse gas cycles from polar firn bubbles.
AAs annual snowfall compacts under its own weight across the East Antarctic Plateau, porous firn gradually seals off microscopic pockets of ancient air at depths of eighty metres. Drilling continuous three-kilometre ice cylinders allows paleoclimatologists to sample pristine pre-industrial atmospheres.
BBy pairing oxygen isotope ratios in frozen water molecules with carbon dioxide concentrations extracted by crushing ice under vacuum, researchers confirmed tight coupling between glacial cycles and greenhouse forcing over eight consecutive ice ages.
Write ONE WORD ONLY: Compressing Antarctic snow seals off air bubbles at depths of eighty _______.