Strange as it may seem, yes, glacier remains can be found in permafrost. This is what a team of researchers from Laval University and UQAR (in particular) discovered on Bylot Island, in the Canadian high Arctic, we read in a scientific article published last September in Geology.
These are the remains of an ancient glacier, and probably very ancient. Its age has not yet been established with certainty, but it could be as old as 2.5 million years, making it “potentially the oldest glacier ice buried in permafrost in the Northern Hemisphere.” the article states. It is because they were buried in eternally frozen ground that these pieces of glacier would have survived the warming of several degrees which took place since the last glacial maximum, which dates back only 20,000 years – and possibly several other glaciation-deglaciation cycles.
“We do not yet really know the extent of what ice remains,” says Stéphanie Coulombe, researcher for the federal government and first author of the study. What we put in the article [c’est-à-dire deux “poches“ de glace d’environ 30 mètres de diamètre par cinq mètres d’épaisseur, enfouies sous quelques mètres de sédiments]this is really the minimum size. We assume it’s much bigger than that.”
It happens that pieces of contemporary glaciers “bury” themselves under permafrost. Above, Glacier C-93, on Bylot Island, has clearly uplifted enough sediment to “self-bury” itself on its margins. (Stéphanie Coulombe)
The remnant was able to be detected because the ongoing melting of permafrost caused a landslide that left some of the ice exposed. The researchers were able to establish that it was indeed an ancient glacier by the fact, in particular, that S-shaped patterns could be seen there, which would be imprinted in the ice by the intense forces of a flowing glacier.
At least, “we think that it is due to the movement of the glacier because we often see that on contemporary glaciers,” says Ms. Coulombe.
His team also did chemical and isotopic analyzes (atomic nuclei come in different “versions” called isotopes) which showed a composition very similar to that of glaciers in the same region. And since the sediment above showed no signs of disturbance or “holes,” they couldn't have been pockets of liquid water that had flowed there before freezing.
What pole reversal?
Now, the age of these glacial remains has proven a little more difficult to determine — in fact there is still work to be done on this subject.
As Guillaume Saint-Onge, geology researcher at UQAR and co-author of the study, explains, the work made it possible to detect signs of a past reversal of the earth's magnetic field in the layer of sediments which covers the ice. As the last inversion dates back 770,000 years and the sediments must have already started to accumulate at that time, to keep track of it, this gives a minimum age for the ice.
The Bylot Island research camp. Ancient ice was found on the plateau seen behind. (Stéphanie Coulombe)
However, it is not impossible that the inversion detected by the researchers is not the one that occurred 770,000 years ago, but goes back even further. We can indeed imagine a scenario where the traces of the last one would have been erased, in one way or another, but older ones would have survived – it's rare, but it happens.
And it is all the more plausible in the present case, underlines Mr. Saint-Onge, that “what is really interesting in this is that the layer which is directly below the ice [donc juste un peu plus vieille]it is a fossil forest [qu’on connaît parce qu’elle avait été étudiée dans des travaux antérieurs] which is around 2.6 million years old.
Further studies will need to be carried out to find out for sure.
One thing is certain, however, this old mirror will open a new window on the past. “It is certain that the archives of very old ice that we now have are quite limited to Greenland and Antarctica,” says Ms. Coulombe. This could allow us to better understand the coverage of the glaciers of the time. […] There have been around twenty glaciations over the last few million years, but we know very little about how these ancient glaciations covered the territory.
The year 2024 was rich in discoveries for the capital's scientific community. Each in their own field, researchers from the region have written new chapters in scientific history. The Sun presents to you, one per day, the most significant breakthroughs of the year.
– Dec 23 : Hormone party (with surprise guest)
– Dec. 24 : The DNA packager
– Dec 25 : Glacier «on the rocks»
– Dec 26 : Soon “organic” electrodes?
– Dec 27 : The family will wait…
