(CNN) — An international research team has successfully drilled and retrieved a 9,186-foot-long (2,800-meter-long) ice core from Antarctica that dates back 1.2 million years. The sample extended so deep that it reached the bedrock beneath the Antarctic Ice Sheet.
The core, nearly as long as 25 soccer fields end to end or six and a half times taller than the Empire State Building to the very tip of its antenna, is a “time machine” that captures “an extraordinary archive of Earth’s climate,” said Carlo Barbante, coordinator of the Beyond EPICA, or European Project for Ice Coring in Antarctica, team that collected the core.
The team has sliced the core into 3.2-foot (1-meter) pieces stored in insulated boxes so they may be studied, said Barbante, professor at Italy’s Ca’ Foscari University of Venice and senior associate member of the Institute of Polar Sciences of the National Research Council of Italy.
The core was collected from Little Dome C, one of the harshest and most extreme locations on the planet. The site is 21 miles (34 kilometers) from the Italian-French Concordia research station and is constantly slammed with strong wind gusts and near-constant temperatures below minus 40 degrees Fahrenheit (minus 40 degrees Celsius).
The ice, some of the oldest drilled on Earth, could provide answers to the biggest remaining questions about how the planet’s climate has changed over time.
“The air bubbles trapped within the ice core provide a direct snapshot of past atmospheric composition, including greenhouse gas concentrations like carbon dioxide and methane,” Barbante said via email. “By analyzing these, we can reconstruct how Earth’s climate responded to changes in climate forcing factors, such as solar radiation, volcanic activity, and orbital variations. This data helps us understand the intricate relationship between greenhouse gases and global temperature over hundreds of thousands of years and now down to 1.2 million year(s) and hopefully beyond.”
Scientists are also hoping the ice will shed light on what caused the timing of Earth’s ice ages to shift suddenly about 1 million years ago, an event that nearly caused the extinction of ancient human ancestors, according to recent research.
An icy milestone
Researchers collected the core during the fourth campaign of the Beyond EPICA — Oldest Ice project, funded by the European Commission. The campaign took place over the most recent Antarctic summer between mid-November to mid-January. Overall, experts from 12 European scientific institutions have spent more than 200 days drilling and processing the ice during the last four summers.
The program builds on the goals of the initial EPICA project that took place from 1996 to 2008. During that time, researchers drilled a deep ice core that unearthed links between climate and atmospheric greenhouse gases over the past 800,000 years. The core collected during the latest campaign marks a new milestone, creating a continuous record of Earth’s climate that dates back even further.
Studies of the original EPICA core showed that Earth’s climate experienced a 100,000-year cycle of cold glacial periods, or ice ages, interspersed with warmer periods. But this finding didn’t match up with marine sediments that revealed Earth once experienced 41,000-year glacial periods prior to 1 million years ago.
The Beyond EPICA project began in 2016 with the goal of finding older ice that could point to why this shift occurred, and the search for the right site started with the use of radar surveys.
Radio echo sounding technologies helped team members zero in on ice that might contain the time capsule they were looking for, said Frank Wilhelms, principal investigator in the field and joint professor at Göttingen University and the Alfred Wegener Institute in Germany.
“We needed a Goldilocks site — ice thick enough for a well-resolved climate record at the greatest depth, but not too thick that the oldest ice had already melted away,” said Dr. Robert Mulvaney, a glaciologist and paleoclimatologist at the British Antarctic Survey.
“This can happen when the heat escaping from the Earth’s mantle is trapped by a thick insulating blanket of ice. If the ice is too thick, we can lose the lowest and oldest layers of ice to melting,” Mulvaney said. “That’s why we spent a lot of effort in surveying the candidate areas to find the right site before drilling started.”
Little Dome C is high on the central Antarctic plateau, reaching an altitude of 10,498 feet (3,200 meters) above sea level, presenting numerous challenges. The team had to work to prevent drill failures and ensure that the electromechanical core drill was progressing through the ice layers. Each meter of ice can contain as many as 13,000 years of climate data, said Julien Westhoff, chief scientist in the field and postdoctoral researcher at the University of Copenhagen in Denmark.
Insights from ancient ice
When the team members retrieved the core, they found what they were looking for. The bottommost 688 feet (210 meters) of the core above the bedrock consists of old ice that has been heavily deformed, likely mixed, refrozen and of unknown origin, the team said.
Analyzing the ice could help to test theories about how it refroze beneath the ice sheet. Researchers will also determine whether even older ice, such as that from the pre-Quaternary Period 2.58 million years ago, is present and provide dating of the rocks beneath the ice to determine when this Antarctic region was last ice-free.
“It was exciting to see the ice age as we drilled deeper, and especially when we knew we were drilling ice older than the EPICA record, which ended at 800,000 years ago,” the British Antarctic Survey’s Mulvaney said in a statement. “This record of 1.2 million years will give us several 41,000-year glacial cycles to compare with the more recent data from the original EPICA core.”
The Mid-Pleistocene Transition, which occurred between 1.2 million and 900,000 years ago, marks the fundamental shift in Earth’s glacial cycles, Barbante said.
“This transition remains a scientific mystery, particularly regarding the role of greenhouse gases and ice sheet dynamics,” he said. “The Beyond EPICA ice core offers an unprecedented opportunity to directly measure atmospheric conditions during this pivotal period, potentially unlocking answers about why this transition occurred and how it shaped our planet’s climate system.”
During the Mid-Pleistocene Transition, ice ages became longer and more intense, leading to a drop in temperature and dry climatic conditions. The global population also dropped to about 1,280 reproducing individuals between 930,000 and 813,000 years ago and then remained that small for about 117,000 years, according to a 2023 study published in the journal Science. The study authors argue this event “brought human ancestors close to extinction,” but others are more skeptical.
Regardless, the ice core could contain evidence as to why the shift in the length of ice age periods occurred.
Something in the air (bubbles)
Ice cores contain layers of snowfall that have been compressed over time, trapping air bubbles and particles that can be analyzed to reveal how Earth’s temperature and atmosphere have shifted.
They could help scientists understand how Earth’s climate has behaved in the past to better predict how things may change in the future — and provide context on how our planet responds to different greenhouse gas concentrations.
“Antarctic ice cores are like Rosetta Stones,” said Jim White, Craver Family Dean of the College of Arts and Sciences at the University of North Carolina at Chapel Hill, in an email. “They are unique in that they speak the language of temperature as well as the language of (carbon dioxide) levels, allowing us to see how these two key climate variables interact.”
White was not involved in retrieving the ice core. But he said the ice has the potential to yield a great deal of information “about the fundamental dynamics of climate change on our planet, and the importance of that cannot be overstated.”
While preliminary analysis occurred at the site, the ice core slices will be transported back to Europe aboard the icebreaker ship Laura Bassi in specialized cold containers to maintain the perfect temperature. Barbante anticipates that the research will be a multiyear endeavor as scientists take a deep dive into measuring concentrations of gas and dust particles within the ice.
Meanwhile, the Beyond EPICA project, as well as other international associations, will search for older ice that could reveal longer climate records. But such efforts will require more advanced technology and planning, Barbante said.
“We have to find other places in Antarctica where we can retrieve continuous climate record(s) similar to the one we are studying,” he said.
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