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Study shows the Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity

Phys.org/news (JANUARY 2, 2019)

Titre : Study shows the Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity

The Sahara desert is one of the harshest, most inhospitable places on the planet, covering much of North Africa in some 3.6 million square miles of rock and windswept dunes. But it wasn’t always so desolate and parched. Primitive rock paintings and fossils excavated from the region suggest that the Sahara was once a relatively verdant oasis, where human settlements and a diversity of plants and animals thrived.

Phys.org/news (JANUARY 2, 2019)

Présentation
Now researchers at MIT have analyzed dust deposited off the coast of west Africa over the last 240,000 years, and found that the Sahara, and North Africa in general, has swung between wet and dry climates every 20,000 years. They say that this climatic pendulum is mainly driven by changes to the Earth’s axis as the planet orbits the sun, which in turn affect the distribution of sunlight between seasons—every 20,000 years, the Earth swings from more sunlight in summer to less, and back again.

For North Africa, it is likely that, when the Earth is tilted to receive maximum summer sunlight with each orbit around the sun, this increased solar flux intensifies the region’s monsoon activity, which in turn makes for a wetter, "greener" Sahara. When the planet’s axis swings toward an angle that reduces the amount of incoming summer sunlight, monsoon activity weakens, producing a drier climate similar to what we see today.

Source  : Jennifer Chu, Massachusetts Institute of Technology

Annonce (Phys.org/news)

Page publiée le 24 juin 2021