Scientists drilling at Prudhoe Dome, a Luxembourg-sized ice bulge in northern Greenland, found it fully melted between 6,000 and 8,200 years ago during early Holocene warming 3-5°C above today. Sediment dating from the 2023 GreenDrill project, published in Nature Geoscience, warns of similar risks from human-driven climate change, with implications for sea-level rise.
A team from the GreenDrill project, co-led by Jason Briner of the University at Buffalo and Joerg Schaefer of Columbia University's Lamont-Doherty Earth Observatory, drilled 1,669 feet (500 meters) through the Prudhoe Dome summit near the former Camp Century base in 2023. They extracted a 7-meter core of sediment and bedrock, using luminescence (infrared) dating to show the surface was last exposed to sunlight 6,000-8,200 years ago. This confirms the dome—comparable in size to Luxembourg—vanished entirely during the early Holocene, when summers were 3-5°C warmer than today.
Lead author Caleb Walcott-George, now at the University of Kentucky, noted the site's past disappearance highlights vulnerability: 'This is very direct evidence that the ice sheet is as sensitive as we feared to even a relatively small amount of warming.' Briner added, 'For natural, mild climate change of that era to have melted Prudhoe Dome and kept it retreated for potentially thousands of years, it may only be a matter of time before it begins peeling back again from today's human-induced climate change.' Schaefer emphasized sea-level insights: 'Rock and sediment from below the ice sheet tell us directly which of the ice sheet's margins are the most vulnerable.'
Supported by the National Science Foundation and involving multiple U.S. universities, GreenDrill targets under-ice sediments in this remote region. The findings align with prior evidence, like a 1966 Camp Century core showing northwestern Greenland ice-free ~400,000 years ago and a 1993 Summit Station sample indicating full ice sheet melt ~1.1 million years ago. Experts not involved, such as Yarrow Axford of Northwestern University, affirmed the sensitivity, while Edward Gasson of the University of Exeter noted it will refine surface melt models. Such melting could contribute tens of centimeters to a meter of global sea-level rise this century, addressing debates on which margins will lose ice first under warming, potentially amplified by Arctic sea ice retreat.
The expedition overcame challenges, including a late fracture nearly halting drilling, resolved by a last-minute equipment switch. Walcott-George described the vast ice as humbling, given its past loss. GreenDrill plans further sample analysis for vulnerability clues and ancient environments.