World’s oldest ice, dated six million years, discovered in Antarctica unlocks clues to a warmer past

World’s Oldest Ice and Air Found in Antarctica Reveal Earth’s Ancient Climate (Image: COLDEX)

A remarkable discovery in East Antarctica has unlocked a 6-million-year-old record of Earth’s ancient climate. Scientists say this frozen treasure, found in the Allan Hills, holds secrets that could reshape our understanding of how the planet cooled over time.

Ancient Ice Offers Glimpse Into Earth’s Past
A team of U.S. researchers uncovered the world’s oldest directly dated ice and air trapped deep within the Allan Hills region. The study, published in the Proceedings of the National Academy of Sciences, confirms the ice dates back six million years, a period marked by much warmer global temperatures and higher sea levels.

The research was led by Sarah Shackleton from the Woods Hole Oceanographic Institution and John Higgins from Princeton University. Both are part of the National Science Foundation-funded Center for Oldest Ice Exploration (COLDEX), a collaboration of 15 U.S. research institutions led by Oregon State University.

Shackleton said the discovery pushes climate research beyond previous limits. “Ice cores are like time machines that let us see Earth’s past. The Allan Hills cores take us further back than we ever imagined,” she explained.

How Did Scientists Date the Ancient Ice?
Through sophisticated isotope analysis, the scientists directly measured the noble gas argon within the ice. The method enabled them to determine the samples' ages with accuracy. The trapped air bubbles offer a rare chance to study atmospheric conditions from millions of years ago.

Ed Brook, director of COLDEX and a paleoclimatologist at Oregon State University, said the findings surpassed expectations. “We thought the ice could be up to three million years old, but what we found was twice that age,” he noted.

Teams working in the Allan Hills spend months drilling through the ice sheet’s edge, where natural conditions preserve ancient layers near the surface. Shackleton said the site’s strong winds and extreme cold prevent fresh snow accumulation, slowing ice movement and helping preserve older layers.

What Do the Findings Reveal About Antarctica’s Climate?
Measurements of oxygen isotopes in the samples showed Antarctica cooled by about 12 degrees Celsius over the last six million years. Researchers say this is the first direct record of long-term temperature change in the region.

John Higgins explained that by dating multiple samples, the team created a “library of climate snapshots” far older than any existing ice core data. These findings will help scientists track greenhouse gas levels and ocean heat changes through history.

COLDEX researchers are now planning further drilling missions in the Allan Hills. Brook said a new phase of exploration between 2026 and 2031 aims to find even older ice, possibly extending Earth’s climate record further back in time.

The project is supported by the National Science Foundation’s Office of Polar Programs, the U.S. Antarctic Program, and Oregon State University. Ice drilling support came from the NSF Ice Drilling Program, with curation by the NSF Ice Core Facility in Denver, Colorado.