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The great threat of sea level rise looms over the world.
The GISP2 ice core was drilled in 1993. Scientists have carefully studied its ice and rock, but no one has looked into the mixed sediments at the bottom. This was because until recently the idea that Greenland was ice-free in the recent geological past seemed far-fetched.
"We saw fossils literally within the first hour, maybe half an hour of working on them," said lead study author Paul Bierman, a professor of environmental sciences at the University of Vermont.
Scientists were surprised to find in the soil layer willow wood, spike moss spores, mushrooms, a complex insect eye and poppy seeds - all of this together indicates the existence of a tundra ecosystem.
If there was no ice in the center of the island, it means its absence in most of Greenland. And this indicates significant problems for the Earth in the conditions of modern warming associated with the use of fossil fuels.
Scientists believe that if greenhouse gas emissions are not reduced, the Greenland ice sheet may melt within the next centuries or millennia. And this will cause the sea level to rise by seven meters.
"Hundreds of millions of people around the world will lose their homes," Bierman said.
The scientists' conclusions are based on two recent discoveries. In 2016, scientists studied the rock from the GISP2 core and concluded that its age does not exceed 1,1 million years. Their simulations also showed that if the ice melted in the center of Greenland, 90% of the island would lose it.
But these findings have been disputed because Greenland was thought to have been covered in ice for the past million years. In 2019, Bierman and an international team re-examined another ice core, this time recovered from the abandoned US military base Camp Century off the coast of Greenland in the 1960s. They found in it not only sedimentary rock, but also leaves and moss.
Using the dating methods available to them, scientists concluded that this ice did not exist until 416 years ago.
The discovery of organic matter in a core taken near the coast prompted Bierman to return to the 1993 core. He wanted to see if he could find similar material. And its detection confirmed what the scientists deduced with the help of models and calculations.
"The ice had to disappear, because otherwise there would be no plants, no insects, no soil fungi. Now we know for sure that the ice disappeared not only in Camp Century, but also in GISP2, right in the center of the ice sheet. We now know that the entire ice sheet is vulnerable to melting," Bierman said.
