6 million-year-old ice discovered in Antarctica shatters records — and there’s ancient air trapped inside
Scientists have extracted a 6 million-year-old chunk of ice from Antarctica – the oldest directly dated ice ever found – and it is helping them reconstruct Earth’s ancient climate.
“Ice cores are like time machines that allow scientists to take a look at what our planet was like in the past,” lead author of the study Sarah Shackletonresearcher at Princeton University and assistant scientist at Woods Hole Oceanographic Institution in Massachusetts, said in a statement. statement. “The Allan Hills cores help us travel much further than we imagined possible.”
The ice and air date from the Miocene (23 million to 5.3 million years ago), when Earth was much warmer, sea levels were higher, and the planet was filled with now-extinct creatures, including saber-toothed cats, okapi-like giraffes, Arctic Rhinoceros and the first mammoths.
Shackleton and his colleagues discovered the record ice in the isolated Allan Hills blue ice area of eastern Antarctica between 2019 and 2023. The Allan Hills ice field is about 6,500 feet (2,000 meters) above sea level, according to the study.
To obtain samples, researchers drilled 330 to 660 feet (100 to 200 meters) deep into an ice sheet. They then dated the excavated ice cores by measuring the radioactive decay of argon isotopes present in the air pockets. Tracing oxygen isotopes in the cores also allowed scientists to determine that the Allan Hills region has experienced consistent cooling of about 22 degrees Fahrenheit (12 degrees Celsius) over the past 6 million years, according to the statement released by Oregon State University, which also participated in the research.
As Antarctica – and Earth as a whole – has steadily cooled over the past few millennia, humans are now rapidly rising global temperatures by releasing large amounts of heat greenhouse gas in the atmosphere. The authors of the new study said that by studying ice cores, they could decipher ancient levels of greenhouse gases and ocean warming, and thus better understand the natural drivers of climate change throughout Earth’s history.
The Allan Hills region preserved the ice through a variety of factors, known and unknown, including the near-static movement of surface ice and rugged mountain features that locked the ice in place.
“We’re still working on the exact conditions that allow these ancient ices to survive so close to the surface,” Shackleton said. “Along with the topography, it’s probably a mix of strong winds and bitter cold. The wind blows away fresh snow and the cold slows the ice to almost a standstill. This makes Allan Hills one of the best places in the world to find old, shallow ice and one of the most difficult places to spend a season in the field.”
