There is a distinction between a geological glacial period, lasting millions of years, and what people commonly call an ice age, with mammoths and smoky caves. We are precisely living in a gentle interlude within a glacial era. And according to a study published in Science, this interlude should have closed long ago.
- The forthcoming glaciation began about 2,000 years ago with the growth of the Barnes Ice Cap, a remnant of the Laurentide
- The ice cap reached its maximum around 1960 before abruptly tipping into mass loss due to the warming of summers
- According to the researchers, human-caused climate warming interrupted this natural glacial cycle and dooms this glacial relic to disappear
- An abrupt halting of an ice age two thousand years ago
- Three kilometers of ice vanished: the geologists’ investigation
- Climate warming, a phenomenon that has altered the course of geological time
An ice age abruptly halted two thousand years ago
Earth has never ceased swinging between extreme cold and periods of temperate respite. Since the planet’s earliest days, at least five glacial periods have come and gone, with episodes of severe glaciation sometimes burying whole continents.
Technically, we are still within a geological glacial era. But for roughly 11,700 years we have enjoyed a milder interglacial, the same one that coincided with the disappearance of a large portion of the woolly megafauna.
That is where the study published in Science shakes our certainties. According to Nicolás Young, a geochemist at Columbia University and the lead author of the work, the next glaciation had indeed begun about 2,000 years ago.
“It was just getting started, everything looked normal, the next glaciation was about to occur, and yet, it stopped,” summarizes the researcher. A abrupt—and, above all, unexpected—braking in a mechanism that was once believed to be perfectly cyclical.
Three kilometers of ice disappeared: the geologists’ investigation
To understand what happened, researchers turned their attention to the Laurentide ice sheet, nicknamed LIS. It was the largest glacial formation of the Pleistocene, dominating the northern part of the North American continent roughly between 95,000 and 20,000 years ago.
At its peak, this ice mass stretched from the Arctic Circle to Illinois. Its thickness could reach up to 3 kilometers, a figure that attests to the colossal giant of which only a remnant remains today.
That remnant is the Barnes Ice Cap, or BIC, the last beating heart of this vanished glacial era. Its bedrock was revealed only in the past decade, offering geologists an unprecedented window into the past.
To date this story precisely, the team cross-referenced two natural clocks. On one side, beryllium-10, an isotope that accumulates in rocks exposed to cosmic radiation and ceases to form once the ice covers them.
On the other, carbon-14, measured in the ancient vegetation revealed by the glacier’s retreat. A plant buried under ice stops absorbing carbon, which allows scientists to determine exactly when it disappeared beneath the advancing ice.
By combining these two methods, the researchers reconstructed a precise chronology. The minimum size was reached 3,600 years ago, a level lower than today’s, and it remained so until about 2,000 years ago.
Climate warming, a phenomenon that has altered the course of geological time
It is precisely at that moment, about 2,000 years ago, that the ice began to advance again. A signal that, according to the researchers, marks the theoretical starting point of the next glaciation.
This growth continued for centuries, in line with the cooling trend that had been underway for millennia in the Northern Hemisphere.
The Barnes Ice Cap reached its historical maximum around 1960. Then, abruptly, the trend reversed. Summer warming tipped the glacier into a negative mass balance: it now loses more ice in summer than it rebuilds in winter.
This shift is not simply a calendar accident. It coincides with the increasing accumulation of greenhouse gases in the atmosphere, a phenomenon that began with the Industrial Revolution, around 1750.
There is a striking paradox here. This industrial pollution began during the middle of the Little Ice Age, the coldest period of the last millennium, whose harsh phase stretched from 1450 to 1850.
According to the researchers, ice losses observed since 1960 can be explained almost entirely by higher summer temperatures. A mechanism that also affects other ice caps in the Canadian Arctic and the North Atlantic.
As for the future, the models are unequivocal. Under current climate profiles, the last vestige of the Laurentide is doomed to disappear. “These will be the very last remnants of the Laurentide, which will disappear for good,” concludes Nicolás Young.
He sums up the magnitude of the observed shift this way: “What was an extremely natural and predictable phenomenon has now disappeared.” A natural cycle, interrupted by a single species.
This study serves as a precise reminder of how human influence on climate now surpasses the planet’s major natural rhythms. We have not only warmed the atmosphere: we have, it seems, erased an entire glaciation before it had a chance to settle in for good.
Sources : Climate Change Stopped the Next Ice Age (lamont.columbia.edu) | Two Thousand Years Ago, a New Ice Age Began—but Human-Caused Climate Change Recently Reversed It, According to New Research (smithsonianmag.com)
Article prepared with the help of AI · Our method
