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January 16, 2008
Glaciation in the super greenhouse?
An interesting item in the online Journal "Science" caught Mausi's eye recently. It seems that a team of scientists have recently discovered that the Antarctic Ice Sheet may well have formed, at least in part, during one of the warmest phases of the earth's history.
It has been commonly held until now that during these super warm phases the poles were ice free. That seems to have been blown literally out of the water by this study which shows that at least the Southern Pole was covered by ice during the Turonian period - the warmest inter glaciation period we have ben able to identify. As Mausi hjas pointed out, it just provces that a lot of these effects are very localised and that it is extremely difficult to draw a single "overall picture" in isolation. As those who have followed my link will see - surface temperatures were , at this period, an average of 35 degrees. And the oceans were nice and warm too.
No doubt we will soon hear from the "Global Warming" lobby that this research is irrelevant. Just as they dismiss the evidence of core samples from the Pacific. I guess an article of faith takes some changing ....
Isotopic Evidence for Glaciation During the Cretaceous Supergreenhouse
André Bornemann,1,2* Richard D. Norris,1 Oliver Friedrich,1,3 Britta Beckmann,4 Stefan Schouten,5 Jaap S. Sinninghe Damsté,5 Jennifer Vogel,1 Peter Hofmann,4 Thomas Wagner6
The Turonian (93.5 to 89.3 million years ago) was one of the warmest periods of the Phanerozoic eon, with tropical sea surface temperatures over 35°C. High-amplitude sea-level changes and positive 18O excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth. New 18O data from the tropical Atlantic show synchronous shifts 91.2 million years ago for both the surface and deep ocean that are consistent with an approximately 200,000-year period of glaciation, with ice sheets of about half the size of the modern Antarctic ice cap. Even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets, calling into question the common assumption that the poles were always ice-free during past periods of intense global warming.
Posted by The Gray Monk at January 16, 2008 03:53 PM
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