- Study shows for the first time that Greenland wasn't covered in ice in the recent past.
- The data comes from long-lost ice cores obtained during a secret army mission during the Cold War.
Drilling thousands of feet down through a giant layer of ice isn't an easy task, but that's what the army liked about it.
Grabbing ice cores for scientists to study served as a perfect cover for their real intention, burying nuclear missiles within Greenland's ice sheet, in a scheme known as Project Iceworm.
The project, which took place during the height of the Cold War, didn't yield the results the army wanted. But by the time they abandoned it in 1967, scientists had gathered enough ice cores to help them understand Greenland's ancient climate.
Along with the ice, scientists grabbed 12 feet of sediment that sat beneath the ice sheet. Most scientists were only interested in the ice, so the sediment cores were labeled, stored away in a bunch of cookie jars, and forgotten.
Not unlike that bag of peas fossilizing at the back of your freezer.
That is until Danish scientists re-discovered the sediment cores in 2018 and shipped them to Paul Bierman, a geologist at the University of Vermont. There, Bierman's then PhD candidate Andrew Christ found something unexpected — signs of life.
They discovered that Greenland's ice had melted in the recent past, which was incredibly surprising, Christ said.
This initial discovery took place over two years ago, but the scientists just now pinpointed when the country's ice sheet had melted. The team of 21 researchers published their findings last week in the journal Science.
Their paper shows that only 416,000 years ago, Greenland's ice sheet had melted and sea levels were between five and 20 feet higher compared to when the sheet was frozen. This means that the current ice sheet is much more sensitive to global warming than previously thought, the scientists reported.
"The ancient frozen soil from beneath Greenland's ice sheet warns of trouble ahead," Bierman and co-author Tammy Rittenour wrote in The Conversation.
More sensitive to warming
The melting occurred way earlier than scientists had predicted. Previous estimates had put a wide window on the thawing, saying it occurred sometime in the last million years.
The Earth naturally cycles through warmer phases and cooler phases, per the Climate Change Resource Center. Shooting back to 416,000 years ago then, we were in a warmer period.
The researchers know this warmer period was caused by normal cycles because they can measure the amount of gases that were present in the atmosphere back then by looking at the molecules that were frozen in the samples.
They determined that greenhouse gas levels were much lower back then than they are today, Christ told Insider.
So if the natural, moderate warming caused the ice to melt, it means the country's ice sheet is more sensitive to temperature changes than scientists originally thought, Christ explained. He and Bierman further said their findings mean the ice sheet is likely going to be sensitive to the changes we've caused to our climate.
Essentially, in the coming centuries, climate change will cause the Greenland ice sheet to melt completely, the researchers said. "It's not going to happen tomorrow. But it's going to happen faster and faster," Bierman said.
This will cause anywhere from five feet of sea level rise to 20 plus feet, the paper reported. What would that amount of water do to a city like Miami, or the island of Manhattan, for example?
Using the National Oceanic and Atmospheric Administration's sea level rise viewer, Bierman showed Insider the consequences.
Slowly, the water eats ups streets, then blocks, then neighborhoods. The viewer maxes out at ten feet, he said, adding: imagine if the water rises higher than that.