Ice cores drilled for missile silo research reveal when Greenland was last green

Long-misplaced ice core samples from an unlikely source — drilled during construction of a U.S. Army base during the Cold War — have revealed that Greenland might have been largely ice-free and covered in plants only a million years ago.

Geologist Andrew Christ and an international group of colleagues suggest this means Greenland's ice cap could be more vulnerable to temperature changes than scientists might have suspected, which they suggest is concerning news in the context of modern climate change.

Today much of Greenland's two million square kilometre area is covered by an ice sheet nearly two kilometres thick — but that ice sheet is melting at an alarming rate.

In a "business as usual" fossil fuel emissions scenario, researchers have estimated that in 200 years enough ice could melt from Greenland to raise sea levels by two metres. This would have catastrophic effects on our coastal cities and infrastructure.

One uncertainty in that estimate that could lead to the ice cap melting more slowly or quickly, is an incomplete understanding of how the Greenland ice cap has behaved in warm periods in the past. 

To understand this better, researchers have been trying to reconstruct the deep history of the ebb and flow of Greenland's ice.

This new study of ice cores, taken from a location in northwestern Greenland in 1966, indicates that the ice cap has largely melted away at least once in the last million years.

"I think that by unlocking this new information, we're able to get a better grasp of what is the threshold in the future that would cause the Greenland ice sheet to melt away and raise sea level," lead researcher and University of Vermont geologist Andrew Christ told Quirks & Quarks host Bob McDonald. 

The findings were published this week in the Proceedings of the National Academy of Sciences.

The science that came in from the cold

The discovery has a backstory with elements from the plot from a cold war spy thriller.

"This ice core sample was collected in the 1960s as part of a military base that was built inside the Greenland ice sheet by the U.S. Army," said Christ. "The Army's original intention was actually to hide nuclear weapons inside the ice sheet."

The effort, called Project Iceworm, included a plan to bury 600 nuclear missiles under the ice as part of armament against the Soviet Union. While that part of the plan was never realized, a base called Camp Century was built, and remains buried under the ice in the northwest of Greenland.

While the military pursued its secret military agenda, scientists brought to help with the construction were very publicly conducting pioneering Arctic research.

"They collected the very first ice core drilled all the way through an ice sheet and at the bottom of about 1.4  kilometres of ice," said Christ. "They recovered three-and-a-half metres of frozen soil."

The 'Holy Grail of ice'

Without the technology to analyze the soil in the 1960s, the samples were stored away and largely forgotten. They spent decades at the University of Buffalo, then found their way to a special ice core sample storage facility in Copenhagen, where they were rediscovered for study in 2017.

Frozen soil from the core was sent to a few geologists in 2019, including Christ, who described it as like working on the "Holy Grail of ice core material."

What Christ and his colleagues saw as they washed the sediment to expose the different sand grains astonished them: mysterious black particles floated in the rinse water.

"We looked at them in the microscope, and they were plant fossils," said Christ. "It was totally amazing."

The fossils were freeze-dried plant remains that included fragments of twigs and leaves from shrubs similar to those currently growing in the Canadian Arctic, he explained.

Christ noted that some of the leaves actually started to unfurl as they were exposed to the rinse water.

"They look like they could have died yesterday."

A warning for today

The soil sample was dated to slightly younger than one million years old, indicating that the ice sheet was absent at that time.

"It means the Greenland ice sheet in this sector of Greenland has melted away in a climate system that was not too different than it has been in the last million years," said Christ. "And that means that that ice sheet is more sensitive to relatively minor changes in climate."

That's not good news for us, he suggested.

"If we just keep going business as usual with carbon emissions, it could be gone in a thousand years; that's seven metres of sea level rise.

"That would be up to two metres of sea level rise in the next 200 years, which would be really bad, really, really bad."  

The melting of the Greenland ice sheet matters (University of Vermont)

U.S. Army film about Camp Century (U.S. Corp of Army Engineers)

Produced and written by Mark Crawley.