6-Million-Year-Old Antarctic Ice Unearthed, Unveiling Earth's Ancient Climate

In a groundbreaking discovery, scientists have unearthed 6-million-year-old ice in Antarctica's Allan Hills, providing an unprecedented glimpse into Earth's ancient climate and atmospheric conditions. This ice, the oldest directly dated on the planet, contains air bubbles that serve as time capsules, offering direct records of the Earth's atmosphere from the Miocene epoch.

The research, led by Dr. Sarah Shackleton of the Woods Hole Oceanographic Institution and Dr. John Higgins of Princeton University, was published on October 28, 2025, in the Proceedings of the National Academy of Sciences. The study reveals a gradual cooling of approximately 12 degrees Celsius (22 degrees Fahrenheit) over the past 6 million years, shedding light on the natural forces driving long-term climate change.

The Allan Hills region of East Antarctica has long been recognized for its unique topography and ice flow patterns that preserve ancient ice near the surface. The research team, part of the National Science Foundation-funded Center for Oldest Ice Exploration (COLDEX), conducted drilling operations in this area to extract ice cores. The age of the ice was determined using precise measurements of an isotope of the noble gas argon, allowing scientists to date the ice directly without relying on surrounding sediments or other indirect evidence.

"Ice cores are like time machines that let scientists take a look at what our planet was like in the past," said Dr. Shackleton. "The Allan Hills cores help us travel much further back than we imagined possible."

This discovery extends the ice core record significantly beyond the previous limit of 800,000 years, providing a rare and direct glimpse into Earth's ancient atmosphere. The analysis of oxygen isotopes in the ice revealed a cooling trend of about 12 degrees Celsius over the past 6 million years, offering the first direct evidence quantifying Antarctica's climate cooling since that ancient warm period. Future research aims to reconstruct concentrations of greenhouse gases and ocean heat levels preserved within the ice bubbles, key clues to understanding the natural forces driving long-term climate change.

"The team has built up a library of what we call 'climate snapshots' roughly six times older than any previously reported ice core data," noted Dr. Higgins.

The findings provide critical context for understanding modern climate change by offering insights into ancient atmospheric conditions and greenhouse gas levels. By studying these ancient ice samples, scientists can better comprehend the natural variability of Earth's climate system and the factors influencing long-term climate trends. This knowledge is essential for improving climate models and predicting future climate scenarios.

The COLDEX team plans to return to the Allan Hills region for additional drilling between 2026 and 2031, aiming to recover even older ice samples and produce a more detailed record of Earth's ancient atmosphere. This ongoing research underscores the importance of Antarctic ice cores in unraveling the complexities of Earth's climate history.

"Given the spectacularly old ice we have discovered at Allan Hills, we also have designed a comprehensive longer-term new study of this region to try to extend the records even further in time," said Dr. Ed Brook, COLDEX director and a paleoclimatologist at Oregon State University.

This discovery not only advances our understanding of Earth's climate history but also highlights the critical role of Antarctic research in addressing global climate challenges.