Greenland – “green land” in Danish – is now only vegetal in name, but a new study shows that the huge arctic island was once ice-free, probably around a million years ago.
This conclusion could be made thanks to the discovery of plant fossils in glacial samples forgotten for decades and found by chance in a freezer in Copenhagen, Dorthe Dahl-Jensen, co-author of the published study, told AFP on Tuesday. in the journal Proceedings of the National Academy of Sciences (PNAS) of the American Academy of Sciences.
“In ice cores, we were able to identify moss, twigs and whole leaves, perfectly preserved, vegetation found on the coast in southern Greenland, but also in the tundra or the boreal forest”, says the professor of climatology at the University of Copenhagen.
These ice cores were taken in 1966 at Camp Century, a secret US base built under the guise of climate research, where 600 nuclear warheads were stored during the Cold War and then removed.
Removed more than a kilometer in the ice, they were then archived in Copenhagen in 1994, without any documentation.
“It was when we changed the freezer that we discovered them, no one had been interested in these 22 samples before,” says Ms. Dahl-Jensen.
Stored at -13 degrees, the sediments are visible to the naked eye. If the fossils cannot be dated with exactitude, the study of isotopes allows a more precise evaluation.
“After measuring the isotopes of water in the ice, we can determine that the ice sheet remained intact and covered Greenland for about a million years,” but that it was ice-free before, according to the professor of climatology.
The study published by PNAS concludes that the huge Greenlandic ice cap “has melted and reformed at least once in the past 1.1 million years.”
Today 85% ice-covered, the largest island in the world – two million km2, nearly 4 times the area of France – lies on the front line of the melting Arctic ice, a region that heats up two to four times faster than the rest of the planet, scientists say.
The latter are particularly worried about a “point of no return” caused by the current global warming, beyond which the melting of the Arctic and Antarctic caps would be irremediable, even if it will certainly take thousands of years.