6-million-year-old ice in Antarctica shatters records — and holds the oldest air samples ever
Researchers in Allan Hills, East Antarctica, recovered 6-million-year-old ice containing the oldest directly dated atmospheric air samples, offering unparalleled snapshots of past greenhouse gases and oxygen isotopes that illuminate Antarctic climate evolution and past warmer Earth conditions.
Key takeaways
- Record‑setting age: The Allan Hills ice yields 6-million-year-old samples with the oldest directly dated atmospheric samples recovered from Antarctic ice.
- Direct dating method: Scientists measured an isotope of argon in trapped air bubbles — a direct age tied to the gas — described by the NSF-funded Center for Oldest Ice Exploration (COLDEX).
- Climate signal: Oxygen isotope analysis shows roughly 12°C cooling in the region over six million years (oxygen isotope analysis).
- Snapshots, not continuous: Samples are discrete climate snapshots rather than a continuous time series; follow‑up field campaigns are planned for 2026–2031 (COLDEX updates).
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How the team found and dated the ice
Location and approach: Field teams worked in Allan Hills, a portion of East Antarctica where wind and ice flow expose ancient layers near the surface. The area acts as a natural time capsule, making old ice accessible without deep drilling.
Direct dating breakthrough: The key advance was measuring a long‑lived isotope of argon trapped in tiny air bubbles. Because argon is inert and the isotope changes at a known rate, the measurement yields an age tied to the gas itself — a more robust approach than inferring age from nearby material (COLDEX report; PNAS study).
What the ice reveals about ancient Earth climate
The samples date to the late Miocene to early Pliocene, when global temperatures and sea levels were higher. Oxygen isotope ratios in the ice record a long‑term cooling of roughly 12°C (about 22°F) over six million years, providing the first direct multi‑million‑year measure of Antarctic cooling (UMaine analysis).
The trapped air bubbles are invaluable: they contain ancient atmospheric gas that lab teams will analyze for greenhouse gases such as carbon dioxide and methane and for tracers of ocean heat and circulation. Those records will let scientists test how atmospheric composition and temperature tracked one another during warmer intervals (COLDEX briefing; UMaine).
Limitations: snapshots, not a continuous record
The newly recovered material does not provide an unbroken timeline. Instead, it offers discrete climate snapshots from different times over millions of years. Scientists will integrate these samples with marine sediments, fossils and younger ice cores to build a fuller picture (COLDEX).
“These snapshots dramatically extend direct atmospheric records well beyond the previous ~800,000‑year limit, filling a major gap in paleoclimate evidence.”
Who led the work and where it was published
The research was led by a 15‑institution U.S. collaboration under the NSF‑funded Center for Oldest Ice Exploration (COLDEX). Principal investigators include Sarah Shackleton (Woods Hole Oceanographic Institution) and John Higgins (Princeton University). The results appeared in the Proceedings of the National Academy of Sciences (October 2025).
What scientists will study next
Laboratory teams are extracting greenhouse gas records from the trapped air, focusing on carbon dioxide, methane and tracers of ocean conditions. The COLDEX team also plans follow‑up field campaigns between 2026 and 2031 to recover additional and potentially older samples (COLDEX plans).
Why this matters to climate science
By extending direct atmospheric records into intervals when Earth was naturally warmer, the Allan Hills samples provide empirical benchmarks for how greenhouse gases, ice sheets and sea level responded to sustained warmth. Those benchmarks will help refine climate models and improve projections used by policymakers and planners.
Implications for San Diego, California
Economic impact: San Diego’s ports, tourism and marine industries rely on accurate sea‑level projections. Better knowledge of past sea‑level responses will inform investments in ports, flood defenses and coastal infrastructure.
Political consequences: The Allan Hills data — direct Antarctic measurements — could be cited in debates about zoning, building codes and state funding for adaptation, strengthening scientific arguments in local planning forums.
Social and cultural effects: Local residents and communities in low‑lying neighborhoods may see research used to justify adaptation projects or insurance changes; clear communication will be essential. San Diego’s outdoor and ocean culture means findings will resonate with educators, museums and recreation groups.
Practical applications: City planners, utility managers and port operators can use refined projections to update flood maps, emergency plans and capital timelines; universities and regional models will translate global science into local actions.
Sources and further reading
- Oregon State University news release: Six‑million‑year‑old ice discovered in Antarctica offers unprecedented window into a warmer Earth
- University of Maine climate change blog: Ice core analysis reveals cooling period 6m years ago
- Proceedings of the National Academy of Sciences paper (DOI)
Ongoing work
COLDEX will continue extracting greenhouse gas records and conducting field campaigns through 2026–2031, with the goal of recovering older and better‑preserved ice. These efforts aim to provide more precise benchmarks of Earth’s response to prolonged warmth — information already relevant to coastal communities from San Diego to the global coastlines.
