Tibetan Ice May Be 128,000 Years Old — and It Rewrites Climate History

Why two sets of cores, drilled 23 years apart, strengthen the case

The team compared ice cores collected from the Guliya Plateau in 1992 and again in 2015. Despite the 23-year gap, the samples showed strikingly similar patterns of oxygen isotopes. That close match tells researchers the ice has preserved a reliable, reproducible climate record.

"Reproducibility of the records within a given ice cap is extremely important," Thompson said. "If you get an identical record a quarter of a century later, it can tell you a lot about the behavior of the ice over time."

The consistency is what gives Thompson the most confidence. "The big picture is that our results tell a very consistent story," he said. "If you get the science right, it's consistent. It's our understanding of what it's trying to tell us that has to catch up."

What changes for climate science?

Ice cores work like tree rings for climate. Snow piles up, compresses into ice, and traps chemical clues about the atmosphere at the time it fell. Read the layers in order, and you get a running history of Earth's climate. But the reading depends entirely on knowing when each layer formed.

That was the old problem at Guliya. Previous research suggested the ice reached back only to the middle of the Holocene — the geological epoch that began roughly 12,000 years ago, after the last ice age ended.

The new evidence changes that picture. At least some of the ice is considerably older than the Holocene. That matters for a big open question: did Tibet's massive ice sheets survive the end of the last glacial period?

"If we only had Holocene-era ice in Tibet, that would mean that the big ice sheets from the last ice age didn't persist through the early Holocene," Thompson said. "But evidence shows that it did."

The ice cap's geography likely explains its longevity. Its high elevation and sheltering terrain probably created conditions that let ancient ice survive through dramatic environmental swings that erased it elsewhere.

What comes next?

The revised timeline opens the door to re-examining the cores themselves. Researchers plan to study additional samples to see how other climate indicators — previously overlooked or misread because the ice's age was underestimated — fit into the longer history.

A firmer timeline also helps answer basic questions about Earth's glacial cycles: when major ice ages began, how long they lasted, and when the ice retreated.

"When did ice start forming on the planet and what did those natural processes of loss look like?" Thompson said. "We need to know those things, and the only way you can really demonstrate it is with accurate time scales on these records."

The research was funded by the U.S. National Science Foundation. Co-authors include Mary Davis and Ellen Mosley-Thompson of Ohio State; Juerg Beer of the Swiss Federal Institute of Aquatic Science and Technology; Christof Vockenhuber and Marcus Christl of ETH Zurich; Tandong Yao of the Chinese Academy of Sciences; and Ninglian Wang and Ling Fang of Northwest University in China.

The takeaway: an old assumption about Tibetan ice just collapsed, and a 128,000-year climate archive is now open for reading.