Sediment from a Cold War military base buried under Greenland’s ice reveals the area was ice-free about 416,000 years ago, with summers 4.7°C warmer than today.
The finding comes from a new study published in Climate of the Past, which analyzed a 3.44-metre sediment core recovered from Camp Century in northwestern Greenland. The site was originally built by the US Army Corps of Engineers in 1959 as a Cold War military base and abandoned in 1967, leaving it buried under accumulating snow and ice. The sediment contained biological markers that allowed scientists to reconstruct ancient environmental conditions.
The biomarkers indicated that the temperature during the months above freezing at the Camp Century site was 4.7 ± 3.2°C higher than the modern reference period. The presence of plant and aquatic biomarkers means the area around the site must have been ice-free, with lakes, streams, and tundra, when the organisms lived. This suggests a dramatically different terrain beneath an area now buried under about 1,387 metres of ice.
It’s striking that a period of moderately warmer temperatures coincided with such a substantial retreat of the ice sheet,
John Michael Aguilar, a postdoctoral fellow at the University at Buffalo
The warm period is known as Marine Isotope Stage 11, which occurred from 424,000 to 374,000 years ago. The researchers noted that while Greenland had experienced similar warmth between 5,000 and 10,000 years ago, the ice at Camp Century did not melt away.
The key difference is believed to be the duration of the warm period; MIS 11 lasted for tens of thousands of years, giving the ice sheet a much longer time to melt and shrink.
The study has significant implications for understanding Greenland’s sensitivity to sustained warming. Today's human-caused warming is more intense than the warm period 400,000 years ago,
said Elizabeth Thomas, the study’s corresponding author. And climate projections suggest that this warmth could persist for hundreds or thousands of years.
It’s really the first bulletproof evidence that much of the Greenland ice sheet vanished when it got warm.
Paul Bierman, one of the researchers involved in the study
The sediment samples were originally extracted during the drilling at Camp Century. It later ended up at the University of Copenhagen, where it remained largely unstudied for over 20 years until it was rediscovered during a freezer cleanout in 2018.
The base itself was a product of Cold War ambition. Constructed in 1959, it was a military experiment with the US Army investigating whether infrastructure could operate beneath the ice. Power came from the Army’s PM-2A nuclear reactor. The larger Project Iceworm plan, which envisioned a concealed network capable of supporting up to 600 nuclear missiles, was proposed to the Joint Chiefs of Staff in 1962. The facility was abandoned in 1967.
The buried base was recently revisited by NASA. In April 2024, NASA scientists flying over Greenland were testing radar equipment when the remains of the abandoned base appeared beneath them. The radar imaging revealed the unexpected presence of the long-abandoned facility beneath the ice during the recent aerial survey of the Greenland landscape.
Earlier coverage: UN Report: Overshooting 1.5C Target Could Cause Permanent Cryosphere Damage
