Scientists have unearthed a remarkable discovery in Antarctica: a 6 million-year-old ice sample – the oldest directly dated ice ever found. This breakthrough allows researchers to reconstruct Earth’s climate from a period significantly earlier than previously possible, providing valuable insights into long-term climate patterns.
Unprecedented Age and Significance
The newly discovered ice is more than double the age of the previously oldest known ice samples, which dated back approximately 2.7 million years. Ice cores are essentially time capsules, allowing scientists to glimpse what the planet was like millions of years ago. The record-breaking ice, along with the air bubbles trapped within, provides a unique window into a past vastly different from the present.
A Glimpse into the Miocene Epoch
The ice and its trapped air date back to the Miocene age (23 to 5.3 million years ago). During this period, Earth experienced considerably warmer temperatures, higher sea levels, and supported a diverse range of now-extinct creatures. These included iconic species like saber-toothed cats, giraffe-like okapis, Arctic rhinos, and early mammoths. Understanding the climate conditions that allowed these species to thrive offers critical context.
The Discovery in Allan Hills
The remarkable ice was discovered in the remote Allan Hills blue ice area of East Antarctica, between 2019 and 2023. This high-altitude region – located approximately 6,500 feet (2,000 meters) above sea level – proved ideal for the preservation of this ancient ice. Researchers extracted samples by drilling as deep as 660 feet (200 meters) into the ice sheet.
Dating the Ancient Ice
Scientists accurately dated the ice cores through a precise technique: measuring the radioactive decay of argon isotopes within the air pockets trapped in the ice. Additionally, analyzing oxygen isotopes provided valuable data confirming that the Allan Hills region has cooled by around 22 degrees Fahrenheit (12 degrees Celsius) over the past 6 million years. This gradual cooling trend offers a long-term perspective on Earth’s temperature history.
Contextualizing Modern Climate Change
While Antarctica – and the Earth – has gradually cooled over recent millennia, human activity is now accelerating global warming by releasing large quantities of greenhouse gases. The researchers hope that by studying these ancient ice cores, they can decipher past levels of greenhouse gases and ocean warming, and thus gain a better understanding of the natural forces that have shaped Earth’s climate throughout history. This knowledge is essential to distinguish natural climate variability from human-induced changes.
The Preserving Factors
The Allan Hills region’s ability to preserve such ancient ice is attributed to a unique combination of factors. These include consistently slow ice movement across the surface, combined with the rugged mountain topography that effectively locks the ice in place. Researchers still continue to investigate the specific conditions responsible for the ice’s exceptional preservation.
“We’re still working out the exact conditions that allow such ancient ice to survive so close to the surface,” Shackleton explained. “Along with the topography, it’s likely a mix of strong winds and bitter cold. The wind blows away fresh snow, and the cold slows the ice to almost a standstill. That makes Allan Hills one of the best places in the world to find shallow old ice, and one of the toughest places to spend a field season.”
The discovery of this 6-million-year-old ice provides invaluable data for scientists studying long-term climate trends and offers a crucial perspective on Earth’s changing climate throughout deep time. This understanding is key to better predicting future climate scenarios and developing strategies to mitigate the impacts of human-induced warming.
