Scientists have recovered a 6-million-year-old chunk of ice from Antarctica – the oldest directly dated ice ever found – and it's helping them reconstruct Earth's ancient climate.
“Ice cores are like time machines, giving scientists a glimpse into what our planet was like in the past,” lead author of the study Sarah ShackletonThis was stated by a researcher from Princeton University and a researcher at the Woods Hole Oceanographic Institution in Massachusetts. statement. “The Allan Hills cores are helping us travel much further back than we ever imagined.”
The ice and air date back to the Miocene (23–5.3 million years ago), when the Earth was much warmer, sea levels were higher, and the planet was filled with now-extinct creatures, including saber-toothed cats, giraffes similar to okapi, Arctic rhinoceroses and the first mammoths.
Shackleton and her colleagues found record ice in the remote Allan Hills blue ice region in East Antarctica between 2019 and 2023. According to the study, the Allan Hills Icefield is located at an altitude of about 6,500 feet (2,000 meters) above sea level.
To obtain the samples, the researchers drilled into the ice sheet to depths ranging from 330 to 660 feet (100 to 200 meters). They then dated the excavated ice cores by measuring the radioactive decay of argon isotopes present in the air pockets. Tracking oxygen isotopes in the nuclei also allowed scientists to determine that the Allan Hills region has experienced a sustained cooling of about 22 degrees Fahrenheit (12 degrees Celsius) over the past 6 million years, according to a statement released by Oregon State University, which also contributed to the study.
While Antarctica – and the Earth as a whole – has been steadily cooling over the past millennia, people are now rapidly rise in global temperature releasing copious amounts of heat-trapping greenhouse gases into the atmosphere. The authors of the new study said that by examining ice cores, they could decipher ancient levels of greenhouse gases and ocean warming and thus better understand the natural causes of climate change throughout Earth's history.
In the Allan Hills region, the ice has been preserved by a variety of factors, both known and unknown, including the nearly static movement of surface ice and the rugged rock formations that held the ice in place.
“We're still figuring out the exact conditions that allow such ancient ice to survive so close to the surface,” Shackleton said. “Along with the topography, it's likely a mixture of high winds and extreme cold. The wind blows away the fresh snow, and the cold slows the ice almost to a stop. This makes the Allan Hills one of the best places in the world to find shallow old ice, and one of the most challenging places to field during the field season.”
