Antarctic ice sheets may be more sensitive to CO2 than we thought

New ice core study helps pinpoint global warming impacts

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Ice core samples suggest that Antarctic ice sheets may see big changes at lower levels of CO2 than previously thought. @bberwyn photo.

Staff Report

After studying a new ice core sample from McMurdo Sound, researchers say they’re a bit closer to one of the holy grails of climate science — understanding how Antarctic ice sheets will respond to increasing concentrations of atmospheric carbon dioxide.

The study, published in the Proceedings of the National Academy of Sciences, suggests that big changes could happen at lower levels of CO2 than previously thought.

The scientists looked at a 3,735-foot sediment core to reconstruct the Antarctic ice sheets’ history in an effort to create a climate model that mirrors conditions during the Miocene Era, when atmospheric CO2 levels were slightly higher, at 500 parts per million, than the 400 ppm level reached just last year, and global average temperatures were about 3 to 4 degrees Celsius higher than today.

“We know that the Antarctic ice sheet will eventually melt if we burn all known fossil fuel reserves, raising sea levels by over 100 feet. What these two studies show is that the Antarctic ice sheet is also vulnerable to much lower levels of carbon dioxide than we thought possible before,” said University of Massachusetts researcher Edward Gasson.

But this does not mean that melting Antarctic ice sheets will raise global sea levels immediately. “The ice sheets will take hundreds of years to respond, so although CO2 may be at the same level as during the Miocene in the next 30 years, it doesn’t mean that they will melt in 30 years,” Gasson added.

Previous attempts to simulate Antarctic ice sheet retreat have been inadequate because despite direct geological evidence that large swings in the extent of ice sheets driven by small changes in atmospheric CO2 occurred, it was difficult for computer simulations to model them.

The new model appears to do a better job at simulating the feedbacks between the ice sheet and climate. The UMass Amherst-led modeling team authors explained out that their work “largely resolves the discrepancy between geological records and ice sheet models that had previously existed.”

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