6-Million-Year-Old Ice Discovered in Antarctica, Shedding Light on Earth’s Ancient Climate

In a groundbreaking discovery, scientists have unearthed 6-million-year-old ice in Antarctica's Allan Hills region, providing the oldest directly dated ice and air samples to date. This find offers an unprecedented glimpse into Earth's ancient atmosphere and climate, significantly enhancing our understanding of historical climate patterns.

The research, led by Sarah Shackleton of the Woods Hole Oceanographic Institution and John Higgins of Princeton University, was published on October 28, 2025, in the Proceedings of the National Academy of Sciences. Both researchers are affiliated with the National Science Foundation-funded Center for Oldest Ice Exploration (COLDEX), a collaboration of 15 U.S. research institutions led by Oregon State University.

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

The Allan Hills region, located in East Antarctica, has long been a focal point for paleoclimatologists due to its unique geological features that preserve ancient ice near the surface. Previous studies in this area have yielded ice samples dating back hundreds of thousands of years, but the recent discovery surpasses these findings significantly. The ice cores were extracted between 2019 and 2023 at elevations around 6,500 feet, utilizing advanced drilling techniques to reach the ancient layers.

The age of the ice was determined through 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. This method confirmed the ice's age as approximately 6 million years, making it the oldest known ice sample to date.

Analysis of oxygen isotopes in the ice revealed a cooling trend of about 12 degrees Celsius (22 degrees Fahrenheit) over the past 6 million years in the Allan Hills region. This data provides valuable insights into the natural climatic shifts that have occurred over geological timescales.

"This is the most significant discovery to date for the NSF-funded Center for Oldest Ice Exploration (COLDEX)," said Ed Brook, COLDEX director and paleoclimatologist at Oregon State University. "We knew the ice was old in this region. Initially, we had hoped to find ice up to 3 million years old, or maybe a little older, but this discovery has far exceeded our expectations."

The discovery offers a rare opportunity to study Earth's climate system during a period when global temperatures and sea levels were significantly higher than today. By analyzing the greenhouse gas concentrations in the ancient air bubbles, scientists can better understand the natural drivers of climate change and improve predictive models for future climatic shifts.

Prior to this discovery, the oldest continuous ice core records extended back approximately 800,000 years. The Allan Hills region had previously yielded ice samples up to 2.7 million years old, but these were not continuous records. The current finding of 6-million-year-old ice sets a new benchmark in paleoclimatology, offering a more extended timeline for studying Earth's climatic history.

The success of this discovery has prompted plans for further exploration in the Allan Hills region. Researchers aim to locate and analyze even older ice samples, potentially extending the climate record beyond 6 million years. These efforts will involve advanced drilling technologies and interdisciplinary collaboration to overcome the challenges of accessing and interpreting ancient ice.

"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, which we hope to conduct between 2026 and 2031," Brook said.

This monumental discovery not only provides a direct window into Earth's ancient atmosphere but also underscores the importance of continued exploration and research in understanding our planet's climatic history and future.