Frozen Archives
Every snowflake that falls on an ice sheet traps a tiny sample of the atmosphere. As snow compresses into ice over centuries, these air bubbles become sealed capsules of ancient atmosphere. By drilling kilometers into Antarctic and Greenland ice sheets, scientists extract continuous records of past climate stretching back 800,000 years — the longest direct archive of Earth's atmospheric composition. Each layer is a page in a book of climate history written by nature itself.
Isotopes as Thermometers
Water molecules containing the heavier oxygen-18 isotope condense more readily than those with oxygen-16. Colder temperatures mean more heavy isotopes rain out before reaching the ice sheet, so the ratio δ¹⁸O in ice decreases with temperature. This relationship, quantified by Willi Dansgaard in 1964, converts isotope measurements into a continuous temperature record. The technique reveals glacial-interglacial cycles with Antarctic temperature swings of 8–10°C over tens of thousands of years.
Trapped Gas Bubbles
At about 60–100 m depth, compressed snow (firn) seals into solid ice, trapping air bubbles that preserve the atmospheric composition at the time of closure. Mass spectrometry measures CO₂, CH⁴, N₂O, and other trace gases directly. The ice core record shows CO₂ oscillating between 180 ppm (glacials) and 280 ppm (interglacials) with remarkable regularity — until the industrial era shattered this pattern with a spike to 420 ppm, unprecedented in 800 millennia.
Reading the Layers
Beyond gases and isotopes, ice cores contain volcanic ash layers (tephra) that provide precise chronological markers, dust concentrations that reveal wind patterns and aridity, sea salt that tracks storm intensity and sea ice extent, and even pollen grains that record vegetation changes. Together, these proxies create a multi-dimensional portrait of past climate. This simulation lets you explore how depth, accumulation rate, and temperature interact to determine the age and climate signals preserved in the ice.