BUFFALO, N.Y. — The site of a former U.S. military base in Greenland was ice-free at a time when summers were a few degrees warmer than today, according to a new University at Buffalo-led study of ancient sediment recovered from beneath the site in the 1960s.
Researchers found that summer temperatures at Camp Century — where the U.S. Army pursued a secret Cold War plan to hide nuclear missiles beneath the ice — were 4.7 degrees Celsius (8.5 degrees Fahrenheit) warmer than modern summers during an ice-free period approximately 416,000 years ago.
For the site to have been ice-free, the Greenland Ice Sheet would have had to retreat more than 60 miles from its present-day edge in that region.
“It's striking that a period of moderately warmer temperatures coincided with such a substantial retreat of the ice sheet,” says the study’s first author, John Michael Aguilar, a postdoctoral fellow at the UB RENEW Institute.
Published Sept. 28 in Climate of the Past , the findings come as scientists project substantial warming across the Arctic in the coming decades. Average annual Arctic temperatures could rise anywhere from 3.3 to 10 degrees Celsius by the end of the century, depending on emissions, according to the Intergovernmental Panel on Climate Change (IPCC).
“This work gives us a better understanding of how the ice sheet responds to sustained warming and what may be possible in the future,” says corresponding author Elizabeth Thomas, PhD, associate professor in the Department of Earth Sciences in the UB College of Arts and Sciences.
Pulled up from nearly a mile beneath the ice sheet during the failed Project Iceworm , the sediment has provided Thomas and her collaborators with important clues about the ancient climate at Camp Century. That includes the evidence that the area was ice-free approximately 416,000 years ago , when the sediment was last exposed to sunlight.
This new study marks the first time the researchers have used the sediment to reconstruct summer temperatures at Camp Century during the ice-free period. In fact, they believe it is the first quantitative estimate of land-based summer temperatures anywhere in Greenland during this ancient warm period. Such estimates have been difficult to obtain because advancing ice sheets subsequently eroded most sediment from that time.
They were able to reconstruct the temperatures by analyzing fatty molecules produced by bacteria and preserved in the sediment.
“The types and proportions of these molecules change depending on the temperature,” Aguilar says. “By comparing them with similar molecules found in modern Arctic lakes, we were able to estimate how warm it was at Camp Century.”
The researchers were somewhat surprised at the results. Greenland experienced similarly warm summers roughly 5,000 to 10,000 years ago, following the last Ice Age. Yet Camp Century remained covered by ice.
This suggests that the duration of warming may be just as important as how much temperatures rise. The warm conditions 416,000 years ago may have lasted much longer — potentially tens of thousands of years — giving the ice sheet more time to melt.
But Thomas cautions that the findings shouldn't be interpreted as reassuring.
“Today's human-caused warming is more intense than the warm period 400,000 years ago,” Thomas says. “And climate projections suggest that this warmth could persist for hundreds or thousands of years. Both the magnitude and duration of warming are important to understanding how the ice sheet will respond.”
The subject of an Emmy Award-winning documentary , the sediment has a long history with UB. It was first brought to the university in 1975 by Chester Langway , who led the ice core drilling at Camp Century. The samples remained in the university’s Central Ice Core Storage Facility and Information Exchange until Langway’s retirement from UB in the mid-1990s.
They then sat largely forgotten for more than two decades at the University of Copenhagen in Denmark until a chance freezer cleanout brought them back to scientists’ attention in 2018.
Thomas, who has been studying the sediment with collaborators from the University of Vermont ever since, says the new study feels like a culmination of her and Aguilar’s work.
“The type of molecular analysis we did in this study is something we do all the time in my lab, but interpreting the results was unusually challenging. We had to account for how the land's elevation changed as the ice sheet grew and melted, which affects how temperatures can be compared across time,” Thomas says. “What may look like a routine analysis actually took years to figure out. It’s been quite a journey, not unlike the journey these sediment samples took to get here.”
Climate of the Past
Experimental study
Not applicable
Holocene-like summer climate during Marine Isotope Stage 11 in northwestern Greenland
28-Sep-2026