Scientists search for climate clues in ancient ice – DW – 08/04/2025
Scientists in Germany are studying a 1.2-million-year-old ice core retrieved from Antarctica after years of planning and months of drilling in temperatures of -35 degrees Celsius (-31 Fahrenheit).
International teams reached depths of 2,800 meters (1.74 miles) into the Antarctic ice sheet to claim the oldest continuous ice core to have ever been drilled. The scientists are now hoping it will unlock vital information about the Earth's climate.
"Ice cores are climate archives, so they tell us something about the climate history of the Earth," said Maria Hörhold, glaciologist at the Alfred Wegener Institute (AWI), where one of the samples is being studied.
The core contains air bubbles allowing scientists to measure the quantities of greenhouse gases, like CO2, held in the atmosphere over the last 1.2 million years.
They hope the ice core could help scientists better understand climate change by shedding more light on the connection between the carbon cycle and the temperatures on the planet.
In past ice core samples, researchers were able to see alternating hot periods with cold, or glacial periods, that took place approximately every 100,000 years. But looking further back, the cold temperatures occurred more frequently — around every 40,000 years.
"This is mainly driven, for example, by planetary features, like how the Earth is positioned towards the Sun," Hörhold told DW. "But people do not really know why we shifted from a 40,000-year cycle at say 1.5 million years ago to what we have today."
By extending the 800,000-year-old ice core record and figuring out why the cycle changed, researchers hope to "improve predictions of how Earth's climate may respond to future greenhouse gas increases," said Liz Thomas of the British Antarctic Survey.
"There is no other place on Earth that retains such a long record of the past atmosphere as Antarctica," added Thomas in a statement. "It's our best hope to understand the fundamental drivers of Earth's climate shifts."
Scientists already know that concentrations of greenhouse gases, like CO2, were lower during colder periods on Earth. While during warmer times, a build-up of greenhouse gases in the atmosphere prevented heat from escaping.
"The idea is that you understand how the climate internally interacts, so how do atmospheric patterns interact, how does ice sheet elevation interact with sea level, and so on," she told DW, adding that studying the ice core would hopefully improve their understanding of those interactions.
However, she added that even during previous warm periods in Earth's history, CO2 concentrations were much lower than they are today. The current high levels are primarily the result of human-driven global warming, caused by the burning of fossil fuels like oil and gas.
The pan-European ice core study is part of the Beyond EPICA – Oldest Ice project.
The ice sample has been cut into one-meter length pieces. These have now been delivered for processing into smaller sub-samples at organizations including AWI polar and marine institute in Bremerhaven, Germany, and the British Antarctic Survey in Cambridge, UK.
To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
But Hörhold said it will take at least a year for the first findings to be published, while other discoveries would likely take longer.
Still, for scientists like Hörhold, who have been part of the Oldest Ice project for years, the retrieval of the ice core is an exciting new chance to discover more about the Earth.
"For every one of us, this was very special; to have that ice in our hands and to know that this is really old and an unprecedented ice core record," said Hörhold. "It's a real honor for us to be responsible for processing here."
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