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Re: P/T extinction linked to global warming

>The warming also meant that polar oceans were not cooled as much as they are 
>today, and the convection cycle that circulates cold, oxygen- and 
>nutrient-rich water between the poles and the tropics was slowed and even 
>stopped, according to the second paper by a team of researchers led by Kliti 
>Grice of the Curtin University of Technology in Perth, Australia.
>"This has devastating effects on the marine organisms that rely on oxygen and 
>nutrients to survive," the team said in an e-mail. "In the worst-case . . . a 
>major part of the water column above the sea floor is devoid of oxygen."

I think the import of Grice's findings have been widely underplayed. They found 
that anoxia in surface waters (the photoic zone where photosynthesis can take 
place) was widespread in the Paleotethys. Basically, the ocean died, and 
released hydrogen sulfide, poisoning marine organisms. Recovery took millions 
of years. The effects on land were secondary, reflecting the lower extinction 
levels that Ward reports. 

Their published paper is rather brief, but she believes that greenhouse 
emissions from the Siberian traps volcanoes tipped the balance, causing 
circulation collapse in the Paleotethys leading to an ecological collapse. 
Their work needs more documentation and elaboration, but it may point us toward 
a potential explanation for the P-T extinctions.
Jeff Hecht, science & technology writer
jeff@jeffhecht.com; http://www.jeffhecht.com
Boston Correspondent: New Scientist magazine
Contributing Editor: Laser Focus World
525 Auburn St., Auburndale, MA 02466 USA
v. 617-965-3834; fax 617-332-4760