[font face=Serif][font size=5]Ancient global cooling gave rise to modern ecosystems[/font]

September 26, 2016

[font size=4] Sea surface temperatures dipped dramatically during a period from 7 million to 5.4 million years ago, a time of massive global ecological change.[/font]

[font size=3]PROVIDENCE, R.I. (Brown University) — Around 7 million years ago, landscapes and ecosystems across the world began changing dramatically. Subtropical regions dried out and the Sahara Desert formed in Africa. Rain forests receded and were replaced by the vast savannas and grasslands that persist today in North and South America, Africa and Asia.

Up to now, these events have generally been explained by separate tectonic events — the uplift of mountain ranges or the alteration of ocean basins — causing discrete and local changes in climate. But in a new study, a team of researchers has shown that these environmental changes coincided with a previously undocumented period of global cooling, which was likely driven by a sharp reduction in atmospheric carbon dioxide.

The research, led by a Brown University geologist and published in Nature Geoscience, is based on a newly developed record of global sea surface temperatures spanning the past 12 million years. The record reveals a distinct period of cooler sea surface temperatures spanning 7 million to 5.4 million years ago, the end of the Miocene epoch. The global climate during the Miocene is known to have been much warmer than the present. During the cool period detected in this study, sea surface temperatures dropped to near modern levels.

“This is the first time the late Miocene has been put in a context of global sea surface temperatures, and we were surprised to see the amount of cooling we found,” said Timothy Herbert, professor in the Department of Earth, Environmental and Planetary Sciences at Brown, who led the study. “In light of this temperature change, the paleobiological observations from this period start to make a lot more sense.”

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