A new scientific study has revealed that Greenland’s ice sheet once retreated more than 60 miles (97 kilometres) from its present edge around 416,000 years ago, exposing land that is now buried beneath nearly a mile of ice. Researchers estimate that summer temperatures in the region were approximately 4.7 degrees Celsius warmer than today offering important insights into how Greenland’s ice responds to prolonged warming.
The study led by researchers at the University at Buffalo and published in the journal Climate of the Past on September 28, 2026, reconstructed ancient temperatures using sediment recovered from beneath Camp Century a former US military installation in northwestern Greenland.
Cold War Military Site Holds Clues to Ancient Climate
The discovery began with sediment samples collected during drilling operations at Camp Century in the 1960s. The site was associated with Project Iceworm a secret US Army plan to construct an underground network capable of housing nuclear missiles beneath Greenland’s ice.
Researchers recovered sediment from approximately 1.6 kilometres below the ice surface. Earlier investigations established that the material had last been exposed to sunlight around 416,000 years ago, indicating that the ice sheet had retreated substantially during that period.
In the latest research scientists examined preserved fatty molecules produced by bacteria in the sediment. The types and proportions of these molecules change with temperature, allowing researchers to reconstruct past summer conditions by comparing them with similar compounds found in modern Arctic lakes.
The analysis suggests that summers at Camp Century were around 4.7 degrees Celsius warmer than present day conditions.
Duration of Warming May Be as Important as Temperature
One of the study’s most significant findings is that the length of a warm period may be crucial in determining how much an ice sheet retreats.
Researchers noted that Greenland experienced similarly warm summer conditions approximately 5,000 to 10,000 years ago following the last major glacial period. However, Camp Century remained beneath the ice during that time.
A possible explanation is that the warm period 416,000 years ago lasted much longer, potentially for tens of thousands of years. This would have allowed the ice sheet more time to melt and retreat.
Elizabeth Thomas, an associate professor of Earth Sciences at the University at Buffalo and corresponding author of the study, said the findings improve scientific understanding of how Greenland’s ice sheet responds to sustained warming.
Ancient Ice Loss Raises Questions About Greenland’s Future
The findings carry implications for the future of Greenland’s ice sheet as the Arctic faces further warming.
According to climate projections cited in the study, average annual Arctic temperatures could increase by 3.3 to 10 degrees Celsius by the end of this century depending on future greenhouse gas emissions.
Thomas cautioned that present day human driven warming is more intense than the ancient warm period and could persist for hundreds or even thousands of years. Both the intensity and duration of warming will influence how the ice sheet responds.
The research therefore highlights the importance of understanding not only how high temperatures rise but also how long they remain elevated.
The sediment samples themselves have an unusual research history. After being collected by scientist Chester Langway, they were brought to the University at Buffalo in 1975. Following his retirement in the mid-1990s, the material spent more than two decades largely overlooked at the University of Copenhagen in Denmark.
A freezer cleanout in 2018 brought the samples back to scientific attention. Researchers from the University at Buffalo and the University of Vermont subsequently began examining their potential to reveal Greenland’s ancient environmental history.
The latest study provides what researchers describe as the first quantitative estimate of summer temperatures on land in Greenland during this ancient warm period.
By uncovering evidence of substantial ice retreat and reconstructing the temperatures associated with it the research offers a valuable record for understanding Greenland’s climatic history and assessing the long term consequences of continued global warming.