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Antarctic history suggests ice sheet ‘danger’ threshold

Carbon dioxide levels above 600 parts per million could induce rapid melting, analysis finds

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2:00pm, March 10, 2016
Matusevich Glacier

TIPPING POINT  A new record of the Antarctic ice sheet’s formation suggests that carbon dioxide levels in the atmosphere could soon reach a tipping point that will make the ice sheet more vulnerable to melting. That includes ice in East Antarctica, such as Matusevich Glacier (shown).

Assembling a detailed timeline surrounding the Antarctic ice sheet’s inception around 34 million years ago, scientists have identified a carbon dioxide “danger zone” for the ice sheet’s demise.

Based on CO2 levels when the ice sheet formed, the researchers report that Antarctica’s ice will be “dramatically” more vulnerable to melting once CO2 surpasses 600 parts per million in the atmosphere. Concentrations of the greenhouse gas reached 400 ppm last year, well above its 280 ppm preindustrial level.

“With present-day emission rates, it’s expected that we’ll reach 600 ppm before the end of this century,” says study coauthor Simone Galeotti, a paleoclimate scientist at the University of Urbino in Italy. The ice sheet stockpiles enough water to raise sea levels by around 60 meters and reshape Earth’s coastlines.

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