2023-09-14 08:31:36
It was previously thought that the birth of the largest desert in the world occurred at the same time as the glaciation of Greenland 2.6 million years ago. However, a series of numerical climate simulations covering the last 30 million years pushes back the date of aridification of the Sahara by more than 5 million years.
A Franco-Norwegian team which includes researchers from the Climate and Environmental Sciences Laboratory (LSCE) (CEA/CNRS/UVSQ) and of theStrasbourg Institute of Globe Physics (CNRS/University of Strasbourg), relied on a series of numerical climate simulations covering the last 30 million years to determine the start of aridification in this region of the globe.
According to their results, the Sahara was formed 11 to 7 million years ago, with the progressive disappearance of the Tethys paleo-ocean which produced the aridification of North Africa and part of the Arabian Peninsula. . Tethys was an ocean located east of Africa for 250 million years. Today only remnants remain, such as the Caspian Sea and the Black Sea.
The withdrawal of Tethys, under the action of plate tectonics, during the Tortonian (-11 to -7 million years ago) would have considerably weakened the summer monsoon in Africa, leading to aridification across North Africa. This change would also have amplified the sensitivity of the African monsoon to orbital forces, mainly the precession of the equinoxes. In Africa, this greater sensitivity translates into oscillations between “Green Sahara” and “Yellow Sahara”.
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