Climate Change Reverses Barnes Ice Cap Growth in Canada

Rising temperatures driven by human-caused climate change reversed the growth of Canada's Barnes Ice Cap around 1960, potentially interrupting an early stage of glaciation, according to research published in the journal Science. The findings suggest that greenhouse gas emissions have altered natural climate processes in the Arctic, although scientists disagree on whether a new ice age had actually begun.

The Barnes Ice Cap, located on Baffin Island in Nunavut, is the last remnant of the enormous Laurentide Ice Sheet, which covered parts of North America approximately 20,000 years ago and reached thicknesses of up to two miles in some areas. Researchers found that the ice cap reached its smallest extent about 3,000 years ago before beginning to expand roughly 2,000 years ago as temperatures cooled.

Nicolás Young, a geochemist at the Lamont-Doherty Earth Observatory within Columbia Climate School and a co-author of the study, said the expansion appeared to signal the beginning of another glacial period. However, the ice cap began shrinking as summer temperatures increased around 1960.

"It was just getting started, everything was normal, the next glaciation was about to happen — and yet it stopped," said Nicolás Young, a study author and geochemist at the Lamont-Doherty Earth Observatory.

The research team examined preserved mosses near the ice cap's edge and analyzed their ages to reconstruct the ice's historical movements. Because the ice cap remains frozen to the underlying bedrock rather than sliding across it, the advancing ice preserved plants that would otherwise have been destroyed or displaced.

Young described the significance of the preserved vegetation in explaining how researchers reconstructed the ice cap's expansion.

"It's a very powerful example of how we have jolted the system," said Nicolás Young.

The scientists also analyzed nearby rocks for a rare radioactive isotope that accumulates when rock surfaces are exposed to the atmosphere. Together, the evidence helped establish when the ice retreated and subsequently advanced.

Young said the timing of the reversal coincided with a substantial increase in human greenhouse gas emissions.

"We think that it's no coincidence that that's at the same time as we've pumped an extraordinary amount of greenhouse gases into the atmosphere," said Nicolás Young.

He characterized the influence of climate pollution on regional cooling processes using two separate descriptions.

"Essentially overpowered," said Nicolás Young, describing climate pollution's influence on natural cooling mechanisms.

Young also referred to the natural processes that would otherwise lower temperatures in the region.

"Want to make that region cool," said Nicolás Young, describing those cooling mechanisms.

Meredith Kelly, an earth sciences professor at Dartmouth College who was not involved in the research, praised the methods used to establish the ice cap's historical movements.

"Novel radiocarbon dating of plants," said Meredith Kelly, describing one of the techniques used in the study.

Kelly said the findings about the ice cap's expansion could be correct but noted that comparisons with glaciers in other regions would help researchers understand the mechanisms involved.

Andrey Ganopolski, a physicist at the Potsdam Institute for Climate Impact Research, offered a different interpretation. He said other climate modeling studies, including his own, suggest the next ice age would not be expected for approximately another 50,000 years, even without global warming.

Ganopolski challenged the interpretation that the Barnes Ice Cap's growth established the beginning of a new glacial cycle.

"Is insufficient to support the conclusion that a new glacial cycle had already begun and was subsequently aborted," said Andrey Ganopolski, a physicist at the Potsdam Institute for Climate Impact Research.

Young and his co-authors maintain that the initial expansion of the Laurentide Ice Sheet can mark the beginning of a glacial period without requiring enormous ice sheets to form first. Their interpretation also offers a different perspective on 1970s discussions about possible global cooling, including a Newsweek article titled "The Cooling World," which warned of a potential food crisis as temperatures fell.

Young said the new findings provide context for those earlier concerns about cooling.

"A new glaciation actually had started; it was just getting going, and now it's stopped," said Nicolás Young, describing the interpretation supported by the study.

However, Young cautioned against interpreting the research as evidence that global warming has eliminated an imminent threat to humanity.

"Saved humanity from an ice age," said Nicolás Young, describing an interpretation that he cautioned readers not to draw from the findings.

He emphasized that glacial periods develop over thousands of years and that the Barnes Ice Cap would have needed substantial additional growth before reaching a size capable of affecting everyday human life.

Young also addressed the potential long-term implications of rising greenhouse gas concentrations for future glaciation.

"We've probably put off any chance of any other future glaciation for a very, very long time," said Nicolás Young.