Engineering: Bipolar glaciation 41 million years ago is a myth

Current thinking called into question.

Large continental ice sheets did not exist in both hemispheres during the warmer-than modern conditions of the time.
 
University of Southampton's School of Ocean and Earth Science at the National Oceanography Centre (NOCS) reported in Nature that the Eocene epoch (55 – 35 million years ago) was the last sustained period of global warmth in Earth’s history.
 
The scientists believe that this global warmth was a likely consequence of atmospheric carbon dioxide levels much higher than today.
 
It is widely thought that the ice sheets on Antarctica were first expanded to its modern size at the end of the Eocene era.
 
However, the recent controversial opinion states that despite the high global temperatures of the time, very large ice sheets existed eight million years earlier, not just on Antarctica but also in the Northern Hemisphere.
 
NOCS researchers’ findings show that if the ice sheets did actually exist eight million years earlier then they must have been small and would have been easily accommodated on Antarctica with no need to include Northern Hemisphere glaciation.
 
This idea 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 had Antarctica sitting over it while the North Pole only had the Arctic sea.
 
The NOCS group also identifies a short-lived event immediately preceding the controversial interval during which ocean temperatures briefly increased, the deep ocean became more acidic and the carbon cycle was disturbed by the contribution of isotopically light carbon to the ocean/atmosphere system.
 
This insight suggests that the operation of carbon cycle processes common to those thought responsible for the famous transient extreme warming events that occurred between 50 and 55 million years ago, providing a focus for future work aimed at better understanding climate-carbon cycle feedbacks.
 
The University of Southampton team based at the NOCS used stable isotope analysis of fossil shells of foraminifera (microscopic marine organisms) and bulk sediment from deep-sea sediments to generate a record of climate change and estimate potential global ice volumes in the Eocene.
 
Sediment cores were taken in the tropical Atlantic Ocean by the Ocean Drilling Program (ODP).
 
The Natural Environment Research Council funded this research via a UK ODP (Ocean Drilling Programme) grant.

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