A new study published in Science (October 22, 2026) by researchers including Nicolás Young and Joerg Schaefer of Columbia’s Lamont- Doherty Earth Observatory (part of the Columbia Climate School) finds that the last remnant of the Laurentide Ice Sheet began expanding about 2,000 years ago, potentially marking the start of the next glacial period, but reversed and began retreating around 1960 due to rising temperatures linked to human- caused warming.
The Barnes Ice Cap on Baffin Island (Nunavut, Canada), roughly the size of Delaware and the final surviving piece of the vast Laurentide Ice Sheet that once covered much of Canada and parts of the northern United States, reached a minimum size after about 3,600 years ago.
It then began re- expanding around 2,000 years ago as the climate cooled enough for net ice accumulation. The researchers interpret this renewed growth as the onset of the next glaciation (what is commonly called an “ice age”), even though a full continental- scale ice sheet would have taken many thousands of years (on the order of ~30,000 years) to rebuild.
Key methods and evidence
- The ice is frozen to the bedrock (not sliding), which preserved vegetation (mosses, lichen, etc.) that was overrun and killed as the ice advanced. Carbon-14 dating of these plants, combined with data from other nearby ice caps and exposure dating (e.g., beryllium-10 on rocks), allowed reconstruction of the ice-margin timeline.
- Historic aerial photos and observations show the ice reached a recent maximum around 1960 and has since retreated (margins averaging ~4 meters per year in recent decades), as summer melt began exceeding winter accumulation.
This challenges model- based views that the next glacial inception was still thousands or tens of thousands of years away under natural (Milankovitch orbital) conditions. The team argues the first renewed ice- sheet growth should count as the beginning of a glacial period. The findings also provide retrospective context for 1970s scientific concerns about a coming ice age: the process had in fact begun, though it would have been gradual and not immediately noticeable.
The paper (“Late Holocene reexpansion of the Laurentide Ice Sheet”) attributes the post- 1960 reversal primarily to anthropogenic greenhouse- gas forcing overwhelming the natural cooling trend from declining summer insolation.
Models suggest the Barnes Ice Cap will disappear entirely within the next few centuries, removing a key nucleation point that historically helped ice sheets expand during cooling phases. Future glacial cycles, if they occur under elevated greenhouse-gas levels, may therefore unfold differently.
In short, the study presents observational evidence that human- driven warming interrupted an emerging glacial period that had already begun in the Arctic remnant of the last major North American ice sheet.
Late Holocene reexpansion of the Laurentide Ice Sheet | Science
Editor’s summary
Has anthropogenic warming prevented the next glacial cycle? Young et al. examined the Barnes Ice Cap (Baffin Island, Canada), the last remaining piece of the Laurentide Ice Sheet (LIS), once the largest Pleistocene ice sheet covering much of North America.
After shrinking through much of the early- and mid- Holocene, the LIS began growing again around 2000 years ago but started shrinking once more around 1960. The authors attribute this reversal to anthropogenic greenhouse forcing and present it as evidence that humans caused the termination of the next glaciation.
Abstract (key points)
- During interglacials, the Laurentide Ice Sheet retreats to Arctic Canada and reaches a minimum configuration. Its subsequent reexpansion marks the start of the next glaciation.
- The Barnes Ice Cap (the last remnant of the most recent LIS) reached its minimum interglacial size after ~3.6 thousand years ago.
- It then reexpanded beginning ~2000 years ago, which the authors interpret as the onset of the next glaciation.
- This renewed LIS reached maximum dimensions around 1960 CE.
- After that, anthropogenic summer warming produced a negative mass balance, ice-margin recession, and the termination of the next glaciation.
- This occurred despite ongoing natural decline in summer insolation, illustrating the dominant influence of anomalous greenhouse- gas forcing.
Main findings and methods
The Barnes Ice Cap sits on relatively low- elevation bedrock (~500 m) and is largely cold- based (frozen to its bed), so it preserves rather than erodes underlying vegetation.
Researchers used:
- In situ ¹⁰Be surface- exposure dating of bedrock and erratics to show the ice margin retreated rapidly across the modern forefield and inside the present-day margin at 3.56 ± 0.24 ka BP.
- Radiocarbon dating of entombed vegetation (mosses and woody plants) that was overrun and killed as the ice advanced, then re- exposed by recent retreat. These “kill dates” document the timing and progressive advance of the ice margin toward its ~1960 historical maximum (a clear trimline). Many ages cluster around the coldest part of the Little Ice Age (~1800 ± 200 CE).
The regional snowline first intersected the Baffin plateau landscape around the start of the Common Era, allowing net ice accumulation and the beginning of re- expansion. Growth continued (with pulses during cooler intervals) until ~1960, after which summer warming reversed the mass balance. Between ~1960 and 2022 the margin retreated 200- 800 m.
Broader implications
The authors argue that the first renewed growth of the LIS remnant should be counted as the start of the next glacial cycle, even though a full continental-scale ice sheet would have taken many millennia to develop.
The modern reversal, driven by human- caused greenhouse -gas increases, interrupted that process. The Barnes Ice Cap is projected to disappear within the coming centuries, removing a historically important nucleation site for future ice- sheet growth.
A companion Perspective in the same issue of Science (“Has the next ice age already come and gone?” by Shaun A. Marcott) discusses the results in the context of orbital (Milankovitch) cycles and anthropogenic disruption of the glacial- interglacial metronome.
The paper is currently listed as free access on the Science website.
Journal: Science, Vol. 394, Issue 6822, pp. 455–459
DOI: 10.1126/science.aed3379, www.science.org/doi/10.1126/science.aed3379
Provided: Columbia Climate School
Authors: Nicolás E. Young, Joerg M. Schaefer, and colleagues.
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