PNAS Science Sessions Secrets of Earth's climate in six-million-year-old ice
Jan 12, 2026
Sarah Shackleton, an assistant scientist at the Woods Hole Oceanographic Institution, dives into the secrets of ancient Antarctic ice. She reveals how ice cores can tell us about past climates and the methods used to date ancient air trapped inside them. Shackleton discusses the unique Allan Hills Ice Area, where remarkably old ice is found. The podcast highlights a significant 6 million-year cooling trend and implications of sediment-rich basal ice for understanding climate history. Tune in for a fascinating glimpse into our planet's climatic past!
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Ice Cores Preserve Direct Atmospheric Records
- Ice cores record layered environmental information including temperature and atmospheric composition through trapped air bubbles.
- These bubbles provide direct samples of past atmospheres, letting researchers track greenhouse gases and aerosols over time.
Blue Ice Areas Extend The Ice Record
- Continuous drilled ice cores previously reached ~800,000 years, with a new European core to ~1.2 million years.
- Blue ice areas like Allan Hills allow access to much older, discontinuous ice beyond continuous core limits.
Fieldwork At Allan Hills Is Beautiful But Tough
- Sarah Shackleton described Allen Hills as a beautiful but harsh blue ice site with strong winds and cold conditions.
- She noted the site likely stagnates, trapping very old ice useful for studying past climates.