A prominent ice dome in northern Greenland completely melted around 7000 years ago during a warmer period, according to new research. Scientists warn that similar temperatures could return by 2100 due to human-induced climate change, highlighting the ice sheet's vulnerability. This discovery provides crucial insights into potential future sea level rise.
Researchers have uncovered evidence that the Prudhoe Dome, a large ice bulge in north-western Greenland comparable in size to Luxembourg, vanished entirely about 7000 years ago. By drilling 500 meters through its center, the team extracted a 7-meter core of sediment and bedrock. Infrared dating revealed that surface sand had been exposed to sunlight then, confirming the dome's complete melt during the Holocene epoch.
At that time, local summers were 3°C to 5°C warmer than present conditions. "This is very direct evidence that the ice sheet is as sensitive as we feared to even a relatively small amount of warming that happened in the Holocene," noted Yarrow Axford of Northwestern University, who was not part of the study.
The findings stem from the GreenDrill project, supported by the National Science Foundation and involving multiple US universities. This initiative targets sediments beneath the ice to reconstruct past climates in one of Earth's least explored regions. Earlier work supports the pattern: a 1966 core from Camp Century indicated north-western Greenland was ice-free around 400,000 years ago, while a 1993 sample from Summit Station showed the entire ice sheet had melted as recently as 1.1 million years ago.
The study addresses debates over which parts of Greenland might melt first under warming. It bolsters evidence that northern areas experienced earlier and more intense warming after the last ice age, possibly due to feedbacks like retreating Arctic sea ice releasing ocean heat. "This question is, when have the edges of Greenland melted in the past?" said Caleb Walcott-George of the University of Kentucky, a team member. "Because this is where… the first foot of sea level rise will come from."
Such melting could contribute tens of centimeters to a meter of global sea level rise this century. The research, published in Nature Geoscience, will refine models predicting surface melt. "The thing that this will help is tuning surface melt models. When will we really start to lose this ice?" asked Edward Gasson of the University of Exeter, unaffiliated with the work.