The Prudhoe Dome in northwest Greenland now consists of an ice dome more than 500 meters thick. But around 7,000 years ago, during a warm phase of the Holocene, the region was apparently ice-free. This is shown by ice core drillings that reached down to the sediment beneath Prudhoe Dome. The results suggest that the ice dome is also particularly vulnerable to future climate changes and may therefore contribute to sea level rise.
The Prudhoe Dome stretches over an area of around 2,500 square kilometers in the northwest of Greenland. The huge ice dome is connected to the main part of the Greenland ice sheet and measures around 600 meters at its thickest point. Over the course of past climate fluctuations, the ice sheet in the region has repeatedly expanded and retreated. However, it was still unclear how far it retreated inland during the warmest phases of the past millennia.
Samples from under the ice
“We drilled through 509 meters of firn and ice at the summit of Prudhoe Dome to obtain material under the ice that provides direct evidence of the response of the northwest Greenland ice sheet to the Holocene warm period,” reports a team led by Caleb Walcott-George from the University at Buffalo in the US state of New York. While previous studies had mostly only analyzed the ice itself, Walcott-George and his colleagues also took samples from the underlying sediment.
Analyzes of the top layer of sediment showed that it was last exposed to sunlight around 7,100 years ago. “This means that Prudhoe Dome melted sometime before this time, probably during the early Holocene, when temperatures were about three to five degrees Celsius higher than today,” explains Walcott-George. This is also confirmed by isotope analyzes of the lowest ice layer: They show that no ice remains from the last ice age, which ended around 11,700 years ago. Instead, the entire Prudhoe Dome must have reformed within the last millennia.
Implications for future sea level rise
The results also have an impact on today’s predictions about the stability of the Greenland ice sheet. “If the natural, mild climate change of the early Holocene melted Prudhoe Dome, potentially pushing it back for thousands of years, it may only be a matter of time before it retreats again due to today’s human-caused climate change,” says Walcott-George’s colleague Jason Briner. Forecasts suggest that by 2100, temperatures at Prudhoe Dome could rise to levels similar to when it completely melted.
If Prudhoe Dome melts again, the water masses previously stored as ice will further contribute to sea level rise. The edges of the ice dome are the first to be threatened by warming. The research team has already set up another drilling site on the edge of Prudhoe Dome, where the ice is significantly thinner. “Rocks and sediments beneath the ice sheet give us direct information about which edges of the ice sheet are most vulnerable, which is crucial for accurate local predictions of sea level rise,” explains co-author Joerg Schaefer from Columbia University in New York. “This new field of science provides this information through direct observations and is a milestone in predicting ice melt.”
Source: Caleb Walcott-George (University at Buffalo, New York, USA) et al., Nature Geoscience, doi: 10.1038/s41561-025-01889-9