Washington – An international group of researchers collaborating in the Andrill project, coordinated in Italy by the University of Siena and the INGV, proved that, sometime between 23 to 14 million years ago the Antarctic ice caps retreated in a significant way, well within the Antarctic continent, under CO2 atmospheric conditions similar to those predicted for the coming centuries. The study, just published in the American journal of Proceedings of the National Academy of Sciences (PNAS), shows that the climate of the polar region and the edges of the caps were highly dynamic, with many climate change cycles, with major ice expansions and contractions. In particular, the regions located at high latitudes in the southern hemisphere have been sensitive to relatively small CO2 variations in the atmosphere – between 280 and 500 ppm. The information was obtained by a geological study on the rock cores and sediments from the Andrill-Sms drilling well and a complementary numerical modeling study on the behavior of Antarctic ice sheets. The results confirm those of a study previously published in Nature, which looked at another “hot” period from the past, approximately 5-3 million years ago, when the average temperature at the Earth’s surface was 3 degrees higher than the current average, and the atmosphere had CO2 values similar to those of the present: at that time, the sharp decline in Antarctic ice caps caused the sea level to rise by about 10 meters. (9Colonne)
