Tropical ocean circulation with climate change in East Africa seems to be linked to 2 million years ago.Top-pics TBK / AlamyPeter Menocal old natural history of Eastern Africa for more than a decade, has been mulling evidence for dehydration, as well as the gradual shift in the direction of document open savannahs, grass eating fauna and the increase in the ancestors of modern man. Now the Marine Geologist at Columbia University in New York and his colleagues think it below a culprit for the shift in climate have fixed: the tropical seas. Menocal team be possible Conference in Santa Fe results at the American Geophysical Union last week.
The breakthrough came after Menocal the shells of planktonic foraminifera analyzed (minute single-celled organisms) in an old sediment core drilled in the Indian Ocean on the West coast of Australia. This calcifying organisms living on the surface of the ocean and increase their intake of magnesium at a predictable rate than the water temperature rises. He and his team found that millions of years old, increase the magnesium content of the foraminifera, the bowls in sediments around 2, indicating the start of a warming trends on this side of the Indian Ocean. This trend auseinandergelaufen much of a significant cooling trend already on the other side of the Ocean off the East coast of Africa documents.
This divergence is approximately 20,000-year wet-dry cycle, which caused by natural tumble due to variations in solar energy in addition to one and elliptical orbit of the Earth is visible. "It is a monster signal," says Menocal.
This shift of the sea surface temperature in the Indian Ocean came at a critical time, at the same time with a quick uptick in the drying process of East Africa, as well as the beginning of modern transport trends in the Pacific Ocean1. Menocal suggested that the Indian Ocean to explain the climate shift about East-Africa trends could and ruled out with a few Modeller at Yale University in New Haven, the theory to test. Alexey Fedorov and Chris Brierley ran a series of experiments analyze the effects of the tropical sea surface temperature produce changes on a global climate model and found that the combination of the one estimated Indian and Pacific Ocean of temperature trends 30-80% reduction of in rainfall over East Africa inspired, which reduce the size depending on the exact.
"What we found that to get the changes in East Africa, you know, the right conditions in the Indian Ocean and must in the Pacific," Fedorov says.
Christina Ravelo, a Palaeoclimatologist at the University of California, Santa Cruz, gets the results "pretty tough" but says that they must be kept in the context. Details are still worked out, she says, but the climate and oceans experienced a long cooling trend, the Pliocene end warm period between 2 and 4 million years ago as the world-the latest analog warmed to a world of greenhouse gases - and entered the ice ages. "The 2 - million-year event is when things started looked like today, but the transition was a long time in the making,", she says. "But it could be it modern of the creation of ocean gradient, which Africa drying out helped."
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Given the tropical climate in happens the rest of the world that this shift as the ice ages is drives, according to Fedorov as centrally for Earth's history. Theories about the cause of the transition between tectonic movements which has changed ocean circulation to the climatic shifts of carbon dioxide driven, but so far none of them taken. "We still do not understand why it happened," says Fyodorov.
It is clear that the East African history together is for Menocal. He says "at least on drying climate, I think, we, who have now nailed". The next question is whether this climatic shift to some of the evolutionary changes can be bound, which seem about the same time, including the appearance of Homo erectus and adapted to the grasslands of life animals arise.
"There are a number things happens around this time, and it is with this great change in climate," says Menocal. "But we do not prove, that it is linked."
Wara, M. W., Ravelo, A. C. & Delaney, M. L. Science 309, 758-761 (2005).If you something offensive or inappropriate or that otherwise are not met our conditions or Community guidelines, select you the appropriate "this comment report" Link.Kommentare on this thread are marked according to the time of booking.This is a public forum. Please keep to our community guidelines. You can be controversial, but please you understand personal or offensive and keep it short. Keep in mind that our threads are for feedback and discussion - not for testing publishing, press releases and advertising.
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