Reconstruction of Antarctica’s formation offers clearer picture of carbon dioxide threat

Science News : The Antarctic ice sheet formed around 34 million years ago. A new study of ocean sediment cores has given a detailed history of the size of the sheet during that period of formation. Combining those data with information about atmospheric carbon dioxide levels at the time provides a better understanding of the effect that CO₂ has on the growth of the sheet. Simone Galeotti of the University of Urbino in Italy and colleagues tracked the ebbing and flowing of the ice sheet in the sediment core and found that when CO₂ levels were above 600 ppm, the ice sheet was confined to land and susceptible to large changes in size due to solar heating. When levels fell below 600 ppm, the ice sheet expanded significantly, which lowered sea levels, and it was no longer as sensitive to solar thermal fluctuations. The findings suggest that an atmospheric CO₂ level of 600 ppm in the Antarctic represents a dangerous threshold that could trigger the rapid loss of ice.