Frozen soil that was collected Greenland During the Cold War, a covert military operation hid another secret: buried fossils that could be a million years old. Recent analysis revealed that plants were so well preserved that they “look like they died yesterday,” researchers said.
US Army scientists excavated the ice core in northwest Greenland in 1966 as part of Project Iceworm, a secret mission to build an underground base with hundreds of warheads where they would be within range of the Soviet Union . A Arctic research station called Camp Century was the military’s cover story for the project. But Iceworm hissed; the base was abandoned and the ice core was forgotten in a freezer in Denmark until it was rediscovered in 2017.
When scientists examined the nucleus in 2019, they discovered fragments of fossilized plants that may have bloomed 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 sometime in the past million years – possibly in the last few hundred thousand years – much of Greenland was ice-free.
Related: Images of melt: the disappearing ice of 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 proves that most of Greenland’s ice has disappeared relatively recently, that doesn’t bode well for the stability of the current ice sheet in response to man-made climate changeIf all of Greenland’s ice melted, the seas would rise by about 24 feet (7 meters), the National Oceanic and Atmospheric Administration (NOAA) reported in 2019. That would be enough flood coastal cities worldwide, the researchers wrote in the new study, published in March. 15 in the diary Proceedings of the National Academy of Sciences
Cold War science
The US Army Corps of Engineers began construction of Camp Century in 1959, and scientists BL Hansen and Chester Langway Jr. supervised the extraction of a 3.4 meter ice core from a depth of 1368 meters below the ice. After the military ended Project Iceworm, the core went into storage, first at the State University of New York in Buffalo, where Langway was a researcher, and then at the Niels Bohr Institute in Copenhagen, said Andrew Christ, lead author of the new study. . and a postdoctoral researcher and lecturer in the Department of Geology at the University of Vermont in Burlington.
“The bottom of the ice core is these frozen chunks of sediment, about four inches [4 inches] long and 10 inches wide, “Christ told Live Science.” They put them in glass cookie jars and called them ‘Camp Century sub ice’ – then forgot about them. It wasn’t until 2017, during an inventory of bound materials for a new freezer, when facility curator Jørgen Peder Steffensen recognized the long-lost core samples. He immediately contacted researchers about examining the sediments for the first time since the 1960s. Christ said.
“When we found the fossils, it was one of those scientific ‘Eureka!’ moments, it was totally unexpected, ”Christ told Live Science. As they rinsed the frozen ground to sort it into grains of different sizes, they saw “little black things” floating in the water. Christ put some of the floating dots under a microscope, “and boom! There were fossil twigs and leaves in this frozen sediment,” Christ said. The best way to describe them is freeze-dried. When we pulled them out and put a little water on them, they sort of unfolded so that they looked like they died yesterday. ‘
Such plants – possibly native to a boreal forest – could only grow in Greenland if the island’s ice sheet had largely disappeared, so the next step was to find out how recently that happened, the study authors wrote.
Buried climate cues
To date the plants, the scientists looked at isotopes (variants of the same element with different numbers of neutrons) from aluminium and beryllium, which build up in minerals when exposed to radiation that filters through the atmosphere. These isotopes can tell scientists how long minerals have been exposed to the surface and how long they have been buried underground.
Based on isotope ratios, the study authors determined that the soil – and the plants that grew in it – last saw sunlight between a few hundred thousand and about a million years ago, the researchers reported. Traces of leaf wax in the core deposits resembled those of current tundra ecosystems in Greenland, according to the study.
The environmental isotope oxygen-18, found in ice trapped in sediment pores in the core, offered further clues about this ancient ecosystem. Oxygen-18 in the core sediments was 6% to 8% higher than the mean during the latter part of the Holocene eraOne explanation is that it came from precipitation-penetrating soil at lower elevations, because widespread ice cover was scarce.
“We definitely had an ice-free northwest of Greenland at the time,” said Christ.
Based on geologic data and ocean geochemistry, scientists estimate that the current Greenland ice sheet was more or less the same size for about 2.6 million years, the study authors wrote. However, their new findings show that ice almost completely disappeared from Greenland during at least one period of the island’s most recent deep freeze period, setting a previously unknown threshold for the stability of the ice sheet.
Scientists already warn that Greenland is accelerating to a critical tipping point in ice loss, predicting that winter snowfall will stop replenishing seasonal melt by 2055, Live Science reported in February.
“This is important as we move forward to a warmer future,” said Christ. “Our climate system is in a delicate balance. If it changes enough, you could melt away large areas of these ice sheets and raise sea levels – and that would inundate and flood large areas of the most densely populated areas on Earth.”
Originally published on Live Science.