Ice core

An ice core is a cylindrical sample drilled from a glacier or ice sheet. Its successive layers preserve evidence of past climate and atmospheric conditions.

Ice-sheet stratigraphy: The study of the ordered layers within ice sheets and what they reveal about accumulation and change. Annual and event layers provide the sequence that gives many cores their chronology.
Paleoclimatology: The study of past climates using natural archives and geological evidence. Ice cores are among its most direct archives of temperature and atmospheric history.
Willie Dansgaard: A Danish geophysicist who pioneered the use of oxygen isotopes in precipitation and ice cores to study climate. His isotope work established a way to infer past temperatures from ice.
Tree-ring dating: A dating method that counts and matches annual growth rings in trees. Tree rings can resolve individual years, while many ice-core records are less finely resolved.
Ice-core dating: Methods for assigning ages to layers and materials preserved in ice cores. Dating connects depth in a core to a timeline of past conditions.
Atmospheric carbon dioxide: Carbon dioxide present in Earth's atmosphere, measured across both modern and ancient records. Air trapped in ice reveals how its concentration changed before direct measurements.
Claude Lorius: A French glaciologist whose Antarctic research helped establish the climate value of trapped air in ice. His work helped show that ancient ice bubbles preserve past atmospheric gases.
Marine sediment core: A cylindrical sample of seafloor sediment that preserves layers of particles and biological remains. Sediment cores extend climate records beyond ice-covered regions but often have different dating and resolution limits.
Stable-isotope analysis: Measurement of isotope ratios to infer the sources, temperatures, and histories of natural materials. Oxygen and hydrogen isotope ratios in ice help estimate past temperatures.
Greenhouse gas: An atmospheric gas that absorbs and emits infrared radiation, contributing to the greenhouse effect. Core air samples track past concentrations of gases that influence Earth's energy balance.

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