6-million-year-old ice core reveals secrets of early Earth

Scientists have discovered air bubbles dating back up to 6 million years, perfectly preserved in ancient ice in the Allan Hills region of East Antarctica.

The Antarctic ice sample has been directly dated as the oldest ever drilled on Earth, opening a window in time to help humanity look back at the planet's ancient climate - Photo: COLDEX

Antarctica is not only a pristine land of penguins and ice, but also a natural time archive, preserving evidence of millions of years of Earth's climate history in layers upon layers of ice.

This work was led by a team led by Sarah Shackleton (Woods Hole Oceanographic Institution) and John Higgins (Princeton University, USA), part of the COLDEX project - Center for the Discovery of the Oldest Ice. They drilled and collected an ice core estimated to be 6 million years old, far exceeding the initial prediction of only about 3 million years.

According to Ed Brook, director of COLDEX and a paleoclimatologist at Oregon State University, “these ice samples are the oldest climate snapshots humanity has ever had, about six times older than previous ice core data.” Younger samples in the interior of Antarctica only record detailed data ranging from the last few hundred thousand to 800,000 years.

Thanks to the tiny air bubbles "frozen" in the ice block, scientists can measure argon isotopes to determine the age, and analyze oxygen isotopes to deduce the climate temperature during that period.

The results show that during the Pliocene, 6 million years ago, the Earth was significantly warmer than it is now, with higher sea levels, but then entered a cold period that lasted millions of years, with global temperatures dropping by about 12°C (22°F).

The discovery helps scientists better understand the planet's natural transitions between warm and cold cycles, and provides valuable data to compare with current warming trends caused by human-caused climate change.

According to the research team, ancient ice cores not only contain water ice, but also "capture" primordial air bubbles, almost the only direct sample that helps humans analyze ancient atmospheric composition, including greenhouse gas concentrations such as CO₂ and CH₄.

By reconstructing past greenhouse gas levels and ocean temperatures, scientists can more accurately predict how Earth will respond to current climate change.

The COLDEX team said it would continue drilling deeper at Allan Hills between 2026 and 2031, with the aim of finding even older ice that could push back the “time record” by millions of years.

"With these spectacular ancient ice sheets, we are slowly opening the door back to the planet's distant past, and each released gas bubble is a piece in the story of Earth's climate evolution," Ed Brook shared.

Ice cores from Antarctica and Greenland have long been a key source of data for paleoclimate studies. They allow scientists to read the Earth’s “record” through layers of compressed snow, inferring greenhouse gas concentrations, dust levels, pollen counts, and even traces of past volcanic eruptions.

The discovery of this 6-million-year-old ice sample, published in the prestigious scientific journal Proceedings of the National Academy of Sciences (PNAS ), marks a major step forward in the field of paleoclimatology.

And who knows, in those air bubbles released after millions of years, there may be a "whisper" of the early Earth, reminding us that understanding the past is the key to protecting the planet's future.

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MINH HAI

Source: https://tuoitre.vn/loi-bang-6-trieu-nam-he-lo-bi-mat-trai-dat-thuo-so-khai-20251104125621754.htm