Earth’s next glacial period began roughly 2,000 years ago, yet human-driven greenhouse gas emissions halted the process by the 1960s. New research in Science uses radiocarbon-dated moss samples from beneath Baffin Island’s Barnes Ice Cap to reconstruct the timing of this interrupted ice age.
Moss Reveals Ice History
The Barnes Ice Cap is a remnant of the Laurentide Ice Sheet that once covered much of North America. Paleoclimatologists led by Nicolás Young of Columbia University’s Lamont-Doherty Earth Observatory found patches of long-dead moss and small shrubs emerging from beneath the ice at its retreating margins.
These plants were alive when the climate cooled, only to be killed by advancing ice. Paleoclimatologists led by Nicolás Young of Columbia University’s Lamont-Doherty Earth Observatory used radiocarbon dating on these kill dates
to map the expansion of the ice margin.
The data indicates the ice cap began to grow 2,000 years ago, signaling the start of a new glacial period. These mosses were growing on the landscape and then all of the sudden the ice cap expands and covers them,
Young explained. That radiocarbon age tells you the timing of when ice killed the plant.
Human Activity Halts Cooling
Human activity has fundamentally altered the pattern of Earth’s orbital cycles, which historically nudged the planet toward cooler climates. The ice cap reached its maximum extent around 1960. It has retreated since, with edges pulling back an average of 4 meters per year since 1980.
Without greenhouse gas forcing, we would be moving slowly but steadily into an ice age, with more and more permanent snow and ice on the land and expanding sea ice in the Arctic Ocean.
Gifford Miller, Institute of Arctic and Alpine Research fellow
In the 1950s and 1960s, early studies described the Barnes Ice Cap as exceptionally stable. Those observations captured the ice cap during a rare moment of equilibrium, where decreasing summer sunlight and rising greenhouse gases momentarily balanced out.
Ending the Glacial Cycle
In the 1970s, some researchers warned of an imminent ice age, a claim later used by climate skeptics to question the reality of global warming. The new study confirms a cooling trend was underway, but it was overwhelmed by human-induced warming.
The Barnes Ice Cap is likely to disappear entirely within the next few centuries. Because this ice cap acts as the seed from which the Laurentide Ice Sheet historically regrew, its total loss could remove the foundation required for future continental glaciation on a natural timescale. The research validates that a glaciation period was beginning, but demonstrates that human influence has effectively ended the cycle.