Mystery of the Earth's Polar Caps 41 Million Years Ago, Solved
For most of our planet's history until fairly recently, the overall pattern has been for the Earth to be hot, with no permanent ice to be found anywhere.
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.
Researchers of the Ocean Drilling Program (ODP) Expedition 207 explored and sampled the Central Atlantic’s Demerara Rise in January and February of 2003. Using pinhead-sized fossils (foraminifera) – collected from sediments deep beneath the Atlantic Ocean, 380 km north of Suriname, South America, they concluded that large continental ice sheets did not exist in both hemispheres around 41 million years ago.
This result is more in keeping with other geological records and climate model results suggesting that the ice sheets were more likely to form earlier in the Southern Hemisphere than in the Northern Hemisphere because the South Pole is capped by a continent, Antarctica, whereas the North Pole is capped by the Arctic Ocean.
“The beauty of the new results," explained Paul Wilson, of the School of Ocean & Earth Science at the UK’s National Oceanography Center and lead proponent of ODP Expedition 207, "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.”
“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.”
The team's research findings will be published in an article in Nature on August 23rd.
Posted by Casey Kazan.
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