Barnes Ice Cap Study Finds 2,000-Year Advance Ended Around 1960
A Science study led by Columbia's Nicolás Young finds the Laurentide remnant on Baffin Island began re-expanding about 2,000 years ago before warming reversed it near 1960.
The story in focus
Ars Technica reports that a Science study led by Columbia University's Nicolás Young found the remnant Laurentide ice sheet on Baffin Island began re-expanding roughly 2,000 years ago. The advance reversed around 1960 as greenhouse gases rose; the Barnes Ice Cap has since lost its accumulation zone and is projected to vanish within centuries.
- The Laurentide Ice Sheet reached its smallest size about 3,600 years ago, then began re-expanding roughly 2,000 years ago, per the study.
- About 70 percent of the team's radiocarbon dates cluster around 1800 CE, which the authors interpret as a late pulse within a longer advance.
- Barnes' margin has retreated 200 to 800 meters since 1960, exposing mosses killed from about 1000 CE onward.
- In the 1960s and 1970s, about 35 percent of Barnes' surface sat above the snow line; by the early 2000s about 3 percent did, and today none does.
- Under any plausible emissions scenario, the study's models project Barnes will disappear within a few centuries.
Evidence frozen in place
Ars Technica reports that the Barnes Ice Cap on Baffin Island is the last surviving fragment of the Laurentide Ice Sheet, which at its peak buried most of Canada and locked away around 80 meters of sea level. Unlike most glaciers, Barnes is cold-based and frozen to the bedrock, so it preserves the ground beneath it rather than grinding it away.
When the ice retreated, tundra plants colonized the bare plateau; when it returned, it killed and entombed them. The team combined beryllium-10 exposure dating of boulders with radiocarbon dating of moss to reconstruct the ice margin's movement. Beryllium data show the Laurentide had withdrawn to within today's margin by 3,600 years ago.
Because plants older than about 1000 CE remain buried under ice, the team inferred the onset of advance from neighboring ice caps, where nearly 200 kill dates are all younger than 2,000 years.
A reversed cycle
According to the study, declining solar energy at high northern latitudes pushed temperatures down, eventually overcoming a roughly 20 ppm rise in atmospheric carbon dioxide over the same span, and ice began to re-expand. That advance continued until about 1960, when rising greenhouse gas emissions turned Barnes' mass balance negative.
Ars Technica reports that carbon dioxide rose about 12 ppm between 1750 and 1850, another 50 ppm by 1960, and a further 138 ppm by 2024. Today no part of Barnes sits above the snow line, leaving no accumulation zone. Young argues the gases did not spare humanity an ice age so much as interrupt a long, regular cycle.
Why did the Barnes Ice Cap stop advancing around 1960?
The study attributes the reversal to human-caused warming. Carbon dioxide rose about 50 ppm between 1850 and 1960, and by 1960 Barnes' mass balance turned negative, ending an advance that had run for roughly two millennia.
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