19 October 2012

Early Triassic ocean temp reached 40& #176;C

by Will Parker

The end-Permian mass extinction, which occurred around 250 million years ago in the pre-dinosaur era, is believed to have wiped out nearly all the world's species. But scientists have been puzzled by the perplexingly long period - five million years - it took for new species to start appearing after the end-Permian event.

Now, an international team of scientists from the University of Leeds, the China University of Geosciences and the University of Erlangen-Nurnburg (Germany), believe they know why life on Earth took so long to recover. It was simply too hot to survive, suggests their research, with temperatures of 60& #176;C (140& #176;F) on land and 40& #176;C (104& #176;F) at the sea-surface.

"Global warming has long been linked to the end-Permian mass extinction, but this study is the first to show extreme temperatures kept life from restarting in equatorial latitudes for millions of years," said Yadong Sun, lead author of a new study that documents the team's findings.

Sun's work is the first to show water temperatures close to the ocean's surface can reach 40& #176;C - a near-lethal value at which marine life dies and photosynthesis stops. Until now, climate modelers have assumed sea-surface temperatures cannot surpass 30& #176;C.

The study, appearing in the journal Science, represents the most detailed investigation into early Triassic temperatures ever carried out. It involved collecting and analyzing data on the ratio of oxygen isotopes in 15,000 conodont fossils extracted from rocks in South China.

Sun speculates that the high temperatures would have created a very strange world - where it was very wet in the tropics but with almost nothing growing. No fish or marine reptiles were to be found in the tropics, he suggests, only shellfish, and virtually no land animals existed because their high metabolic rate made it impossible to deal with the extreme temperatures. The polar regions would have likely provided the only refuge from the baking heat.

"Nobody has ever dared say that past climates attained these levels of heat. Hopefully future global warming won't get anywhere near temperatures of 250 million years ago, but if it does we have shown that it may take millions of years to recover," noted co-researcher Paul Wignall, from the University of Leeds.

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Source: University of Leeds