Research suggests a new ice age was starting in Arctic Canada until global warming halted it
An ice cap in Nunavut began expanding 2,000 years ago, a sign of a new glacial period, but warming reversed its growth by the 1960s.
A study of an ice cap in Nunavut indicates the next glacial period on Earth had already begun before human-caused warming halted its development. Research published in the journal Science shows the Barnes Ice Cap on Baffin Island started growing again about 2,000 years ago after a period of retreat. The authors argue this renewed expansion marked the start of a new ice age, a process that continued until the 1960s. At that point, rising summer temperatures began to reverse the ice cap's growth, causing it to shrink instead.
"It was just getting started, everything was normal, the next glaciation was about to happen, and yet it stopped," said Nicolás Young, a geochemist at Columbia University's Lamont-Doherty Earth Observatory. "It's a very powerful example of how we have jolted the system." Young and his colleagues studied the Barnes Ice Cap, the last remnant of the vast Laurentide Ice Sheet that once covered much of North America. They sought to determine if this remaining ice had once been smaller before regrowing.
The researchers dated plants that had been preserved under the ice to track its historical expansion. The Barnes Ice Cap is frozen to its bedrock and does not slide, so when it grew it buried vegetation intact. As the ice has retreated since 1960, it has exposed these plants. Using carbon-14 dating, which measures the decay of a radioactive form of carbon in organic material, the team could estimate when the plants were buried and killed by the advancing ice.
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"If you do this enough times, you can actually develop a timeline of that ice margin systematically advancing over plants. You're actually tracking the expansion of that ice margin," said Young. Their analysis, which also included samples from other recently melted small ice caps in the area, showed the Laurentide Ice Sheet was at its smallest about 3,000 years ago. Approximately 1,000 years later, the climate cooled enough for ice to begin accumulating again.
The study proposes that this regrowth should be considered the beginning of a glacial period, a definition that starts much earlier than the formation of continent-spanning ice sheets. This challenges earlier models that suggested the next ice age was tens of thousands of years away. The findings also lend support to claims from some climate scientists in the 1970s that an ice age was approaching. "It actually was happening," Young said. "They couldn't quite prove it, but now we sort of have the evidence."
The natural process would have been imperceptibly slow, with noticeable cooling taking thousands of years and the full continental ice sheet requiring about 30,000 years to reform. Human-driven warming interrupted this cycle near its start. By the 1960s, the Barnes Ice Cap was losing more mass in summer than it gained in winter. Models now project it will melt completely within a few centuries. "That will be the true very last remains of the Laurentide, disappearing for good," Young said.
The loss of this ice cap could alter the future of glaciations. The Laurentide remnant provided a foundation and supported feedback processes that encouraged ice accumulation when the climate cooled. With high greenhouse gas concentrations, it is unclear when another glaciation might begin, and future ice sheets may have to form without this head start. "What has been an extremely natural and predictable phenomenon is now gone," said Young. The study "Late Holocene reexpansion of the Laurentide Ice Sheet" was published on October 22, 2026.
With files from SciTechDaily