A Glacial Cycle Cut Short
“Everything was just beginning, everything was proceeding normally, the next glaciation was on its way—and yet it stopped,” said Nicolás Young, a geochemist at the Columbia Climate School. A new study published in the journal Science confirms that human-driven global warming has effectively halted the onset of a new ice age.
Researchers studying the Barnes Ice Cap on Baffin Island in the Canadian Arctic discovered that this remnant of the massive Laurentide Ice Sheet—which once covered much of North America—had been expanding for nearly two millennia. The Laurentide Ice Sheet, which investigators sought to track across the last 2.6 million years, previously reached thicknesses of up to 3.2 kilometers in the region.
Mapping History Through Ancient Flora
To reconstruct the history of the ice cap, the team examined vegetation frozen beneath the advancing ice. As the ice retreated in recent decades, it exposed these plants, which had been perfectly preserved rather than crushed because the Barnes Ice Cap is frozen to its bedrock. By using radiocarbon dating on 88 new samples and 186 previously published measurements from the region, the scientists mapped the ice cap's steady advancement across the terrain. The team faced a task so complex that researchers likened it to the twelve labors of the mythical hero Hercules, as geological evidence of ice movement is frequently obliterated by time or human land modification.
The data reveals that the ice cap had been shrinking during the Holocene until roughly 3,600 to 2,000 years ago. At that point, the trend reversed. The ice began a period of expansion driven by Milankovitch cycles—long-term changes in Earth’s orbit that reduced summer solar radiation in the Northern Hemisphere.
The 1960 Turning Point
For roughly 2,000 years, the ice grew. Then, around 1960, the trend hit a breaking point. By this time, rising summer temperatures caused by greenhouse gas emissions began to outweigh the natural cooling effect of the orbital cycles. The ice cap, which had reached its maximum extent for that period, began to lose more mass in the summer than it could recover in the winter. These findings provide a measure of validation for climate scientists who, in the mid-20th century, pointed to evidence of an encroaching ice age. “In reality, it was actually happening,” Young emphasized.
This shift suggests the natural progression toward a new glacial period has been interrupted. While previous models suggested the next ice age was thousands of years away, the researchers argue that the early growth of the ice sheet between 2,000 years ago and the mid-20th century represented the true start of a new glacial phase.
Barnes Ice Cap Faces Total Disappearance
The Barnes Ice Cap is the only surviving portion of the Laurentide Ice Sheet, which never completely melted away. The remaining ice is expected to disappear entirely within the next few centuries if current climate trends continue. “These will be the truly last remnants of the Laurentide Ice Sheet, which will vanish forever,” Young noted. “What was an extraordinarily natural and predictable phenomenon is now gone.”
The loss of this ice cap represents more than just a reduction in volume. As an active center for ice accumulation in the past, its disappearance means that any future cooling cycle may play out differently than those in the geological record. Joerg Schaefer, a co-author of the study, noted that the team’s approach allowed them to identify the “first steps” of ice sheet growth preserved in the environment, a process now being reversed by human activity.
Researchers Analyze Ice Cap to Establish Timeline
Why did researchers focus on the Barnes Ice Cap? It is the last remaining fragment of the Laurentide Ice Sheet. Because it is frozen to the bedrock, it preserved the underlying vegetation, providing a reliable record of when the ice advanced and retreated over the last several thousand years.
Scientists established the timeline by radiocarbon dating plants uncovered by the retreating ice. While the study suggests a glacial cycle had begun, the current climate trajectory—driven by human-caused greenhouse gas emissions—has halted that process. Researchers estimate it would take approximately 30,000 years to restore the ice sheet to its former continental scale, even if natural cooling factors were to resume.
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