6 million-year-old ice discovered in Antarctica shatters records — and holds trapped air that reveals Earth’s warmer past
Researchers in East Antarctica’s Allan Hills recovered ice dated to about six million years old, the oldest directly dated ice and trapped air yet found — offering a rare, direct window into Earth’s warmer Miocene–Pliocene climate.
- Oldest directly dated ice: COLDEX scientists recovered ~6 million-year-old ice from Allan Hills, providing unprecedented direct records of ancient atmosphere and climate (Center for Oldest Ice Exploration (COLDEX)).
- Direct-dating via trapped air: Argon isotope measurements in air bubbles give a direct age and reduce uncertainties compared with indirect methods (argon isotope measurements).
- Long-term cooling quantified: Oxygen isotope analyses indicate Antarctica cooled ~12°C (22°F) over the past 6 million years (Oxygen isotope data; see the PNAS paper).
What researchers found and why it matters
A team led by Sarah Shackleton (Woods Hole Oceanographic Institution) and John Higgins (Princeton) drilled and sampled blue ice in Allan Hills and recovered ice that, by multiple dating techniques, is about 6 million years old — roughly six times older than the longest continuous Antarctic ice records previously available. The discovery opens access to periods in the Miocene and Pliocene when global temperatures and sea levels were often higher than today.
The ice contains trapped air bubbles that preserve a direct record of ancient atmospheric chemistry and greenhouse gas levels (trapped air bubbles). These tiny time capsules let scientists measure past concentrations of CO2 and methane and compare them to modern levels to test climate sensitivity during warmer states of the Earth.
How the ice was dated
Dating very old ice is notoriously difficult. Instead of relying on surface stratigraphy or local geology, the team used direct chemical dating by measuring argon isotopes in air bubbles. Because argon isotopic ratios evolve at known rates, the measurements provide an age for the trapped air — and thus the ice — reducing uncertainties tied to indirect methods.
“This technique extends Antarctic records from ~800,000 years to roughly six million years — opening ancient climate secrets.”
Temperature and chemical clues from deep time
Analyses of oxygen isotopes in the ice provide a temperature signal. Those measurements suggest Antarctica cooled by about 12°C (22°F) over the past six million years — the first direct long-term measurement of Antarctic cooling (Oxygen isotope data; see also the PNAS paper).
The trapped air also enables reconstruction of ancient CO2 and methane concentrations. Those greenhouse gas records will help climate modelers evaluate how sensitive Earth’s climate and ice sheets were during warmer intervals and how oceans stored heat when seas were higher.
Why Allan Hills can yield such old ice
Allan Hills is a blue ice area: strong katabatic winds and local topography bring ancient ice near the surface, making sampling possible without deep coring. The Allan Hills site therefore provides accessible windows into ice far older than typical core-based records.
The international team and next steps
COLDEX — the Center for Oldest Ice Exploration — is a 15-institution U.S. collaboration combining field sampling, laboratory analyses, and new dating methods. Field work and lab campaigns will continue: teams plan follow-up expeditions to Allan Hills through 2031 to search for even older ice and expand the record (COLDEX).
Ongoing laboratory analyses will focus on reconstructing ancient greenhouse gas levels and ocean heat content. Those datasets will be critical for testing climate models that predict ice-sheet response, sea-level change, and global climate patterns.
Implications for The Inland Empire, California
Although the discovery is polar and paleo in scope, it has practical local relevance. Improved, longer-term climate constraints sharpen regional projections for precipitation, drought, extreme heat, and sea-level-driven supply-chain risks — information that water managers, farmers, and local governments in the Inland Empire can use for planning.
- Economic impacts: Better models inform planting schedules, crop selection, irrigation investments, and port-related supply-chain risk assessments.
- Policy and planning: Clearer data about past rapid change may encourage updated zoning, water policy, drought contingency, and infrastructure funding priorities.
- Public health and social resilience: Knowledge of past climate extremes can guide cooling centers, heat-mitigation, wildfire preparedness, and community outreach.
- Education and partnerships: Local universities (UC Riverside, Cal State San Bernardino) and research groups could pursue collaborations, internships, and data-sharing with COLDEX researchers.
Future work and what to watch for
Scientists will continue to analyze trapped air to reconstruct Miocene–Pliocene greenhouse gas concentrations. Additional Allan Hills expeditions planned through 2031 aim to retrieve older samples and widen the record. For regional planners and the public, forthcoming results will refine long-term projections and local adaptation choices.
Source material and verification
The discovery and analyses are described in a peer-reviewed Proceedings of the National Academy of Sciences (PNAS) paper and summarized in a Woods Hole Oceanographic Institution press release. An independent summary of the ice-core analysis also appeared at the Climate Change Institute.
For full methods and data, consult the linked PNAS paper and the WHOI news release.
