What it is
During interglaciations, the Laurentide Ice Sheet, the largest of the Pleistocene ice sheets, retreats to Arctic Canada, where it reaches a minimum configuration, and its reexpansion from that minimum marks the start of the next glaciation. The authors show that Barnes Ice Cap on Baffin Island, Canada, the last remaining remnant of the most recent Laurentide Ice Sheet, reached its minimum interglacial dimensions after about 3,600 years ago and then reexpanded from about 2,000 years ago, marking the onset of the next glaciation. This new ice sheet reached its maximum dimensions around 1960 CE, after which human-caused summer warming produced a negative mass balance, retreat of the ice margin and, in the authors' words, the termination of the next glaciation. That this glaciation ended despite the ongoing decline in summer insolation, the solar energy received in summer, illustrates, the authors write, the influence of anomalous greenhouse gas forcing on climate.
Why it matters
The Laurentide Ice Sheet's last remnant regrew from about 2,000 years ago, the authors' sign of the next glaciation, until human-caused warming after ~1960 reversed it. The reexpansion of the Laurentide Ice Sheet from its interglacial minimum marks the start of a glaciation. On Baffin Island, Barnes Ice Cap reached its smallest size after about 3,600 years ago and the peak of its regrowth around 1960 CE; human-caused summer warming then turned its mass balance negative even though summer insolation is still declining, which the authors present as the influence of anomalous greenhouse gas forcing on climate.
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Filed underGeology and Paleoclimatology Research, Cryospheric studies and observations, Climate variability and models