A remnant ice cap on Baffin Island in Arctic Canada began expanding again roughly 2,000 years ago, a shift that stalled in the 1960s as greenhouse gas warming took hold, according to research published in the journal Science and reported by detikInet. The study, led by geologist Nicolas Young of Columbia University's Lamont-Doherty Earth Observatory, examined the Barnes Ice Cap, the last surviving piece of the vast Laurentide ice sheet. detikInet reports that the findings offer fresh insight into how natural climate cycles and human activity can each shape the timing of ice ages.
Why it matters
The Laurentide ice sheet once blanketed most of Canada, with ice up to about 3 kilometers thick. It held enough frozen water that global sea levels sat roughly 80 meters lower than they would if that water were in the oceans, according to the reporting. Almost all of that mass is gone, and what remains on the Baffin Island plateau carries a record of how the ice retreated and then partially returned.
Because the Barnes Ice Cap is frozen directly onto the bedrock beneath it, it does not scour the ground the way glaciers sliding over meltwater do. That quirk of its behavior means plants that grew on the surface were buried and preserved when the ice advanced over them — giving scientists a rare archive of the ice sheet's movements.
Reading the ice's history in rock and moss
Young described the site's significance plainly, telling the outlet through detikInet's account that Barnes is the final remnant of one of the Laurentide ice sheet's domes. According to the reporting, that leftover ice preserves evidence of the environmental changes that unfolded as the larger sheet shrank and then grew back.
To pin down when the ice returned, the team used two independent dating techniques. The first measured beryllium-10 isotopes on exposed rock surfaces. These isotopes build up while rock sits open to cosmic rays, so their concentration indicates how long a surface has been free of ice cover. That method showed the Laurentide ice had pulled back close to its present-day limit about 3,600 years ago, and likely retreated further around 3,000 years ago, detikInet reports.
The second approach relied on plant remains found beneath the ice. Young explained that the plants had been growing normally on open ground until the expanding ice sheet overran them, and the ice killed them outright. Radiocarbon dating of the moss remains establishes what glaciologists call a kill date — the moment the plants were entombed.
By combining dates from multiple locations, the researchers reconstructed how the ice margin shifted over thousands of years. About 70% of the radiocarbon dates clustered around the year 1800, coinciding with the height of the Little Ice Age. Young's team, however, reads that period not as the start of the expansion but as a late stage of a process that had already been underway for about two millennia.
Supporting evidence came from nearly 200 plant dates collected at smaller ice caps on the same plateau, which indicated that ice growth there also began roughly 2,000 years ago. Since Barnes sits close to those sites, the researchers concluded it most likely began expanding on the same schedule, according to the reporting.
Two forces pulling in opposite directions
The study attributes the shift to a tug-of-war between two influences: declining solar energy reaching high northern latitudes and rising atmospheric carbon dioxide concentrations. Solar energy at those latitudes peaked roughly 10,000 to 11,000 years ago, then gradually weakened as changes in Earth's orbit and axial orientation altered how much sunlight the region receives. detikInet's account describes that long decline in incoming solar energy as one driver of the ice's regrowth.
Countering it was the buildup of carbon dioxide in the atmosphere. Around 1960, the balance tipped. Warming driven by rising greenhouse gases reversed the expansion, and the ice cap began losing mass again.
The research adds detail to a broader question about the timing of glacial cycles. Natural orbital forcing had set the region on a path toward renewed ice growth, but the human-driven increase in heat-trapping gases interrupted that trajectory within a few decades.
Watch for further dating work at other Laurentide remnants, which could sharpen the timeline of when the ice's advance began and how quickly industrial-era warming erased it.
