Scientists Discover Six Million Year Old Ice in Antarctica, Offering a Glimpse into Earth's Warmer Past
A groundbreaking discovery has been made by a team of researchers, including experts from Woods Hole Oceanographic Institution (WHOI), who have uncovered the oldest directly dated ice and air on Earth in the Allan Hills region of East Antarctica. This remarkable find, published in the Proceedings of the National Academy of Sciences, reveals a 6-million-year-old ice sample, the oldest ever dated from Allan Hills, providing an unprecedented window into our planet's climate history.
The research, led by Sarah Shackleton, an assistant scientist in Geology & Geophysics, and John Higgins of Princeton University, is part of the National Science Foundation-funded Center for Oldest Ice Exploration (COLDEX). This collaboration of 15 U.S. research institutions, led by Oregon State University, has made a significant breakthrough in understanding Earth's past climate.
Shackleton, who has participated in multiple seasons of ice core drilling at Allan Hills, emphasizes the significance of this discovery: "Ice cores act as time machines, allowing scientists to glimpse our planet's past. The Allan Hills cores enable us to explore much further back than we ever imagined."
This discovery is a major milestone for COLDEX, an NSF Science and Technology Center established in 2021 to explore the vast Antarctic ice sheet, the planet's largest ice mass. COLDEX Director Ed Brook, a paleoclimatologist at OSU, highlights the importance of this achievement, stating it is the most significant discovery to date for the center.
The team's research is part of a friendly competition among various international teams to extend the ice core record beyond its previous 800,000-year limit. Recently, a European team announced finding a deep continuous ice core reaching 1.2 million years in East Antarctica's interior.
COLDEX researchers are exploring a unique setting for old ice. They spend months in a remote field camp in the Allan Hills, drilling one to two hundred meters on the ice sheet's edges. This location combines ice flow and rugged mountain topography, preserving old ice and making it more accessible. In contrast, retrieving the oldest continuous ice cores from East Antarctica sites requires drilling over 2,000 meters deep.
The trapped air in these cores allows scientists to directly date the ice by measuring an isotope of the noble gas argon. This direct dating method provides valuable insights into the ice's age, as it measures properties within the ice itself, rather than inferring age from associated features or deposits.
Despite the non-continuous nature of the records, the researchers emphasize the unprecedented antiquity of the ice. Higgins explains that dating multiple samples has created a 'climate snapshot' library, roughly six times older than any previously reported ice core data, complementing the more detailed younger data from cores in Antarctica's interior.
Temperature records from oxygen isotopes in the ice reveal a gradual long-term cooling of approximately 12 degrees Celsius (22 degrees Fahrenheit) in this region over the last 6 million years. This is the first direct measure of cooling in Antarctica during this period.
Ongoing research aims to reconstruct atmospheric greenhouse gas levels and ocean heat content, which are crucial for understanding natural climate change causes. A COLDEX team will return to Allan Hills for further drilling, potentially obtaining even older ice and more detailed snapshots.
Brook reveals plans for a comprehensive long-term study of this region, aiming to extend records further in time, scheduled for 2026-2031. This ambitious project will build upon the team's groundbreaking discovery at Allan Hills.
The paper's co-authors include Julia Marks Peterson, Christo Buizert, and Jenna Epifanio from Oregon State; Valens Hishamunda, Austin Carter, and Michael Bender from Princeton; Lindsey Davidge, Eric Steig, and Andrew Schauer from the University of Washington; Sarah Aarons, Jacob Morgan, and Jeff Severinghaus from the Scripps Institution of Oceanography at the University of California, San Diego; Andrei V. Kurbatov and Douglas Introne from the University of Maine; Yuzhen Yan from Tongji University; and Peter Neff from the University of Minnesota.
The NSF Office of Polar Programs, the Science and Technology Center Program at the NSF Office of Integrative Activities, and Oregon State University support COLDEX. The U.S. Antarctic Program, funded by NSF, and the NSF U.S. Ice Drilling Program provide fieldwork and ice drilling support, respectively, with ice sample curation handled by the NSF Ice Core Facility in Denver, Colorado.
