Washington: A drop in carbon dioxide (CO2) levels seems to have triggered Antarctic ice sheet formation.
Scientists from Yale and Purdue Universities stumbled on the discovery while examining molecules from ancient algae found in deep-sea core samples.
Matthew Huber, professor of earth and atmospheric sciences at Purdue, said roughly a 40 percent decrease in CO2 occurred prior to and during the rapid formation of a mile-thick ice sheet over the Antarctic approximately 34 million years ago.
"We went from a warm world without ice to a cooler world with an ice sheet overnight, in geologic terms, because of fluctuations in carbon dioxide levels," he added, the Science journal reported.
For 100 million years prior to the cooling, which occurred at the end of the Eocene epoch, earth was warm and wet. Mammals and even reptiles and amphibians inhabited the North and South poles, which then had subtropical climates.
Then, over a span of about 100,000 years, temperatures fell dramatically, many species of animals became extinct, ice covered Antarctica and sea levels fell as the Oligocene epoch began, according to a Yale and Purdue statement.
Mark Pagani, the Yale geochemist who led the study, said polar ice sheets and sea ice exert a strong control on modern climate, influencing the global circulation of warm and cold air masses, precipitation patterns and wind strengths, and regulating global and regional temperature variability.
"The onset of Antarctic ice is the mother of all climate `tipping points,`" he said. "Recognising the primary role carbon dioxide change played in altering global climate is a fundamentally important observation."