6-million-year-old ice in Antarctica’s Allan Hills rewrites the record — and traps ancient air that could sharpen climate forecasts
Allan Hills, Antarctica (High Desert News Online) – Scientists recovered roughly 6-million-year-old ice from East Antarctica’s Allan Hills, the oldest directly dated ice core material yet found, offering rare ancient air samples and temperature indicators that extend paleoclimate snapshots into a warmer late Miocene–early Pliocene world.
- Oldest directly dated ice: Allan Hills samples dated to ~6 million years via argon isotope measurements in trapped air bubbles.
- Ancient atmosphere: Tiny air bubbles preserve greenhouse-gas and trace-gas data from the late Miocene–early Pliocene.
- Temperature signal: Oxygen isotopes show ~12°C (22°F) Antarctic cooling over 6 million years.
- Local relevance: These snapshots can refine climate models used for water, wildfire, and infrastructure planning in the High Desert, California.
Discovery and direct dating
Researchers led by Sarah Shackleton of the Woods Hole Oceanographic Institution and John Higgins of Princeton recovered ice dated to about 6 million years ago in the Allan Hills region of East Antarctica. The find is described in a Woods Hole Oceanographic Institution press release.
How the ice was dated
The team used argon isotope measurements from tiny air bubbles trapped in the ice to directly date both the ice and its enclosed atmosphere — a major advance because most very-old climate records rely on indirect geological markers rather than preserved ancient air.
Snapshot archive, not a continuous record
The Allan Hills material is a set of discontinuous “snapshots”, not a continuous multi-million-year core. Each recovered segment gives a precise look at atmospheric composition and temperature indicators at specific times ~6 million years ago, around the Miocene–Pliocene boundary.
Ancient air and greenhouse gases
Air bubbles preserved in the Allan Hills ice contain samples of the ancient atmosphere, enabling direct measurements of greenhouse gases and trace constituents from a period that predates every continuous ice-core record. These data will be used to test and validate climate models simulating warmer Earth states; summaries of the significance appear in outlets such as IFLScience and a regional synthesis on the University of Maine site (University of Maine climate summary).
Temperature trends and geological context
Oxygen isotope analysis of the Allan Hills ice indicates Antarctica cooled by roughly 12°C (22°F) over the past 6 million years. This provides direct Antarctic evidence for a long-term shift from the warmer late Miocene/Pliocene world toward the cooler Pleistocene glacial cycles, complementing geological and ocean records that suggested higher sea levels and global warmth during that interval.
Why the Allan Hills?
Allan Hills is favorable because local ice dynamics and persistent wind-driven ablation bring very old ice close to the surface, allowing recovery without deep continuous drilling. That surface exposure makes Allan Hills one of the most promising sites for finding still-older ice and expanding the direct atmospheric record.
Collaboration and next steps (COLDEX)
The work was led by the Center for Oldest Ice Exploration (COLDEX), a consortium of 15 U.S. institutions funded by the U.S. National Science Foundation. COLDEX plans additional field seasons and a larger 2026–2031 study to expand the snapshot library and pursue sequences that may approach continuity. See the core announcement in the Woods Hole press release for details.
Implications for the High Desert, California
Practical planning: Ancient-air reconstructions will improve climate-model fidelity used by regional water managers, insurers, and infrastructure planners. More reliable projections support better decisions on reservoir management, insurance premiums, and investments in roads and utilities.
Political and social effects: Locally, clearer, directly measured climate signals can help elected officials and fiscally conservative stakeholders justify targeted spending on resilience. Emergency managers, farmers, and small businesses can use refined scenarios to improve preparedness for wildfire, extreme heat, and water shortages.
Actionable uses:
- Local planning agencies can request updated model projections informed by ancient-air reconstructions to revise hazard mitigation and capital plans.
- County water agencies and utilities can use improved long-range scenarios to justify investments in storage, conservation, and rate structures.
- Fire districts can integrate refined seasonal outlooks into fuel management and staffing decisions.
In their words
“Ice cores are like time machines that let scientists take a look at what our planet was like in the past. The Allan Hills cores help us travel much further back than we imagined possible,” said Sarah Shackleton of the Woods Hole Oceanographic Institution.
Sources and further reading
- Woods Hole Oceanographic Institution press release: Six million–year‑old ice discovered in Antarctica offers unprecedented window into a warmer Earth
- University of Maine climate summary: Ice core analysis reveals cooling period 6m years ago
- IFLScience: The oldest ice ever recovered contains Antarctic air bubbles from 6 million years ago
