New research to test global ice volume approximately 41.6 million years ago shows that ice caps at this time, if they existed at all, would have been small and easily accommodated on Antarctica.
The findings contradict a recent controversial suggestion that Earth was extensively glaciated at this time despite having been much warmer than today, most likely because of high atmospheric carbon dioxide levels. In an article published in Nature on 23 August, researchers using pinhead-sized fossils (foraminifera) – collected from sediments deep beneath the Atlantic Ocean, 380 km north of Suriname, South America – say large continental ice sheets did not exist in both hemispheres around 41 million years ago. Ocean Drilling Program (ODP) Expedition 207 explored and sampled the Central Atlantic’s Demerara Rise in January and February of 2003.
This result is more in keeping with other geological records and climate model results suggesting that the threshold for ice sheet inception would have been crossed earlier in the Southern Hemisphere than in the Northern Hemisphere because the South Pole has a continent sitting over it (Antarctica) whereas the North Pole has an ocean (the Arctic).
Paul Wilson, lead proponent of ODP Expedition 207 explained, “The beauty of the new results is that they resolve a big problem. How can there have been more ice than today during an interval that was much warmer than today? The answer is that there was not more ice – that idea was a mistake based on inadequate data. The results give us renewed confidence in our understanding of the sequence of geological events and thus the controls on ice sheet existence.” Wilson is on the faculty of the School of Ocean & Earth Science at the UK’s National Oceanography Centre, Southampton.
“The research is a classic example of the amazing way in which the Earth System is so intricately integrated,” said co-proponent Dick Norris of University of California, San Diego, Scripps Institution of Oceanography. “Isn’t it a marvelous thing that we can learn so much about the polar continental ice caps by examining tiny fossils that lived on the sea floor at the equator.”
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