Deep within a remote ice cap in northwestern Tibet, scientists have uncovered evidence of a remarkable frozen archive that may stretch back more than 128,000 years. The groundbreaking discovery suggests that ancient ice high in the mountains has somehow managed to survive since the last ice age, offering an unprecedented and extraordinary window into Earth’s ancient climate, atmospheric conditions, and the resilience of high-altitude glaciers.
The findings significantly extend the known glacial record from the region by more than 100,000 years, establishing these samples as the oldest ice cores ever successfully recovered from this specific part of Tibet. Furthermore, they provide rare, tangible evidence of how mountain glaciers managed to endure major, sweeping shifts in Earth’s global climate over millennia.
Researchers reached these extraordinary conclusions by meticulously examining ice cores collected from the sweeping Guliya Plateau during two separate expeditions in 1992 and 2015. Remarkably, despite being drilled a full 23 years apart by different teams, the recovered samples revealed strikingly similar patterns of oxygen isotopes. Scientists routinely rely on these isotopic signatures to reconstruct past environmental conditions, surface temperatures, and precipitation patterns. The remarkably close match between the two sets of samples indicates that the ice cap has preserved a highly reliable and reproducible record of climate history, standing up to decades of scrutiny and technological re-evaluation.
"Reproducibility of the records within a given ice cap is extremely important," said Lonnie Thompson, lead author of the study, professor of earth sciences, and senior research scientist at the Byrd Polar Research Center at The Ohio State University. "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."
How Scientists Dated the Ancient Tibetan Ice
Determining the absolute age of ice that has remained frozen and compressed for tens of thousands of years is a notoriously complex task. To establish a far more accurate and dependable timeline for the Guliya cores, the international research team turned to advanced, specialized dating methods involving radioactive isotopes of beryllium and chlorine.
These naturally occurring radioactive forms of elements decay at strictly predictable rates, making them exceptionally valuable tools for identifying major events deep in Earth’s environmental history. In this case, the researchers utilized these chemical signatures to detect definitive evidence of the Leschamp Geomagnetic Excursion. This dramatic, well-documented disturbance in Earth’s magnetic field occurred more than 41,000 years ago and left distinctive, globally recognized chemical footprints trapped within the accumulating layers of ice.
Following this isotopic confirmation, the team cross-referenced and compared its findings with detailed oxygen isotope records preserved in nearby Tibetan cave deposits, such as stalagmites that also record local climatic shifts. Together, this converging body of evidence strongly suggests that the Guliya ice record extends well beyond 128,000 years into the past, capturing multiple glacial and interglacial cycles.
"It’s a really critical finding, because outside of the polar regions, this is the only ice core we have from the mountaintops that go back that far," Thompson noted. "Records out of Huascarán only go back over 30,000 years, not over 100,000, so that makes Guliya a very unique record."
The full scope of the findings has been published in the peer-reviewed scientific journal Science Advances, drawing widespread attention from the global paleoclimate community.
A Frozen Climate Record From the Last Ice Age
Ice cores remain among scientists’ most powerful and informative sources of direct data regarding ancient global climates. As seasonal snow accumulates year after year and is gradually compressed by subsequent snowfall into dense glacial ice, tiny air bubbles and chemical impurities are trapped within. This process preserves minute atmospheric clues about past temperatures, greenhouse gas concentrations, volcanic eruptions, and broader environmental conditions. By carefully examining these distinct physical and chemical layers, researchers can piece together a high-resolution history of how the planet’s climate changed over thousands or even millions of years.
However, correctly interpreting these complex records fundamentally depends on knowing precisely when each individual layer of ice formed. Without a reliable, well-constrained timeline, even an exceptionally pristine and well-preserved ice core can be difficult to contextualize, leading to potential misinterpretations of past environmental shifts.
That exact uncertainty had previously complicated earlier interpretations of the Guliya ice cap. Past research suggested that its accumulated record reached back only to the middle of the Holocene, the current geological epoch that began nearly 12,000 years ago following the conclusion of the last major ice age.
The new evidence decisively establishes that at least some of the underlying ice is considerably older than the Holocene, dating back through the last glacial period. This revelation also carries profound implications for understanding whether large, vulnerable ice masses in Tibet persisted or completely melted away as the planet emerged from the last glacial maximum.
"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 explained. "लेकिन evidence shows that it did."
What the Discovery Reveals About Earth’s Glacial History
The Guliya ice cap’s unusual geography and topography may help explain how and why it managed to preserve such an exceptionally old climate record. Its extreme high elevation, combined with the surrounding sheltering terrain, likely fostered unique microclimatic conditions that allowed ancient ice to remain frozen in place through major, disruptive environmental changes that wiped out glaciers elsewhere.
Beyond simply establishing the true age of the ice, researchers hope that a much more precise and dependable timeline will help answer fundamental, long-standing questions about the history of Earth’s glaciers. Knowing exactly when major periods of global glaciation began, how long they persisted, and the exact mechanisms and timing of the ice’s retreat is essential for reconstructing the planet’s natural climate cycles and predicting future trajectories.
"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 newly revised timeline also creates exciting new opportunities to investigate the Guliya ice cores in significantly greater detail. Armed with a reliable chronological framework, researchers now plan to study additional core samples to determine how other physical and chemical indicators of past climate and environmental conditions fit into this vastly expanded history.
Those future laboratory analyses could soon reveal critical information that was previously overlooked, misdated, or interpreted incorrectly simply because scientists did not fully understand the true age of the ancient ice beneath their feet.
For Thompson, one of the most encouraging and scientifically validating aspects of the discovery is how consistently the diverse measurements and methodologies continue to support the same overarching interpretation.
"The big picture is that our results tell a very consistent story," he concluded. "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."
The research expedition and subsequent analysis received substantial support from the U.S. National Science Foundation. Key co-authors from The Ohio State University include Mary Davis and Ellen Mosley-Thompson. Additional international contributions came from Juerg Beer of the Swiss Federal Institute of Aquatic Science and Technology; Christof Vockenhuber and Marcus Christl of ETH Zurich in Switzerland; Tandong Yao of the Chinese Academy of Sciences; and Ninglian Wang and Ling Fang of Northwest University in China.
