Frozen ground that was collected in Greenland during the cold war by a secret military operation hid another secret: buried fossils that could be a million years old. Recent scans have revealed plants so well preserved that they “look like they died yesterday,” researchers said.
US Army scientists unearthed the ice core in northwest Greenland in 1966 as part of Project Iceworm, a secret mission to build an underground base concealing hundreds of nuclear warheads, where they would be stored. striking range of the Soviet Union. A Arctic The research station named Camp Century was the Army’s cover for the project. But Iceworm fizzled; the base was abandoned and the ice core was forgotten in a freezer in Denmark until it was rediscovered in 2017.
When scientists studied the core in 2019, they found fragments of fossilized plants that may have flowered a million years ago. Greenland’s current ice cover was thought to be nearly 3 million years old, but the tiny plant fragments say otherwise, showing that at some point in the last million years – possibly during hundreds of thousands of years – much of Greenland was free of ice.
Related: Images of melting: the ice that is disappearing from the Earth
Today, most of Greenland is covered by the Greenland Ice Sheet, which covers 656,000 square miles (1.7 million square kilometers), about three times the size of Texas, according to the National Snow and Ice Data Center (NSIDC).
If the new research holds up and most of Greenland’s ice disappeared relatively recently, that doesn’t bode well for the stability of its current ice sheet in response to human-made attacks. climate change. If all the ice in Greenland melted, the sea would rise about 24 feet (7 meters), the The National Oceanic and Atmospheric Administration (NOAA) reported in 2019. That would be enough to flood coastal cities around the world, the researchers wrote in the new study published in March. 15 in the review Proceedings of the National Academy of Sciences.
cold war science
The U.S. Army Corps of Engineers began building Camp Century in 1959, and scientists BL Hansen and Chester Langway Jr. supervised the extraction of an ice core measuring 11 feet (3.4 meters) from a depth of 4,488 feet (1,368 m) below the ice. After the military shut down Project Iceworm, the core was stored, first at the State University of New York at Buffalo, where Langway was a researcher, then at the Niels Bohr Institute in Copenhagen, a said Andrew Christ, lead author of the new study. and a postdoctoral fellow and lecturer in the Department of Geology at the University of Vermont in Burlington.
“The bottom of the ice core is these pieces of frozen sediment, about 10 centimeters [4 inches] long and 10 centimeters in diameter,” Christ told Live Science. “They put them in glass cookie jars and labeled them ‘Camp Century sub ice’ — then forgot about them. ‘In 2017, during an inventory of related materials for a new freezer, when the facility’s curator, Jørgen Peder Steffensen, recognized the long-lost cores, he quickly contacted researchers to examine the sediments for the first times since the 1960s, said Christ.
“When we found the fossils, it was one of those ‘Eureka!’ moments, it was totally unexpected,” Christ told Live Science. While rinsing the frozen ground to sort it into grains of different sizes, they noticed “little black things” floating in the water. Christ put some of the floating spots under a microscope, “and boom! There were fossil twigs and leaves in that frozen sediment,” Christ said. “The best way to describe them is to freeze them. When we took them out and put some water in them, they sort of uncoiled, so they looked like they were dead. yesterday.”
Such plants – possibly from a boreal forest – could only grow in Greenland if the island’s ice cap was largely gone, so the next step was to figure out when this happened recently. , the study authors wrote.
Buried climatic clues
To date plants, scientists looked at isotopes (variants of the same element with a different number of neutrons) of aluminum and beryllium, which accumulate in minerals when exposed to radiation that filters through the atmosphere. These isotopes can tell scientists how long minerals have been exposed on the surface and how long they have been buried underground.
Based on isotope ratios, the study authors determined that the soil — and the plants growing in it — last saw sunlight between a few hundred thousand and about a million years ago. years, the researchers reported. According to the study, traces of leaf waxes in basal sediments resembled those of present-day tundra ecosystems in Greenland.
The environmental isotope oxygen-18, found in ice locked in the pores of core sediments, offered further clues to this ancient ecosystem. Oxygen-18 in core sediments was 6% to 8% above average during the latter part of the Holocene era; one explanation is that it originated from precipitation permeating the ground at lower elevations, as widespread ice cover was rare.
“We definitely had an ice-free northwest Greenland during this time,” Christ said.
Based on geological records and ocean geochemistry, scientists estimated that the present-day Greenland Ice Sheet persisted at more or less the same size for about 2.6 million years, the authors wrote. study. However, their new findings show that ice disappeared almost entirely from Greenland during at least one period of the island’s most recent deep freeze, presenting a previously unknown threshold for ice sheet stability.
In fact, scientists are already warning that Greenland is accelerating towards a critical tipping point in ice loss, with winter snowfall expected to stop replenishing seasonal melt as early as 2055, Live Science reported. in February.
“It’s important as we move forward into a warmer future,” Christ said. “Our climate system has a delicate balance. If it changes enough, you can melt large parts of these ice caps and raise sea levels – and that would inundate and inundate large parts of the most densely populated areas of the world. Earth.”
Originally posted on Live Science.