A hydroclimatic record from Lake Tanganyika — the second deepest lake in the world — based on the hydrogen isotopic composition of fossil leaf waxes dD wax highlights the major features of the African Humid Period in East Africa Tierney et al. Leaf waxes are ablated from vegetation surrounding the lake and transported by wind and water to the sediments, where they are well-preserved. The dD value of the leaf waxes is a proxy for relative aridity: plants record lower dD wax values when the climate is humid, and higher dD wax values when it is dry.
As in the records of Niger River outflow and Sahara dust flux, the African Humid Period is easily identified in the dD wax record from Lake Tanganyika as the very low dD wax values that occur between 11, and 5, years ago. These low values indicate rainy conditions as well as a potentially greater contribution of rain from the Atlantic Tierney et al.
Like the Sahara dust flux record, the initiation and termination of the humid period at Lake Tanganyika appears to have been abrupt, occurring within a few centuries. One abrupt event that appears to be synchronous across much of North and East Africa is the occurrence of dry conditions during the Younger Dryas period 12,—11, years ago , when cool conditions prevailed over much of the northern hemisphere and particularly over the North Atlantic Ocean Figure 2b-e; Gasse, ; Broecker, ; deMenocal et al.
Climate models have confirmed that reduced North Atlantic temperatures weaken African monsoonal circulation and reduce regional rainfall Tjallingii et al. One of the most fascinating aspects of the African Humid Period is its impact on North African human sustainability and cultural development Hoelzmann et al. The rock art images in Figure 1 depict impressions of this life. Towards the end of the African Humid Period between 7, and 5, years ago the progressive desiccation of the region led to a widespread depopulation and abandonment of North African sites.
These populations did not disappear, however. Adkins, J. Barth, H. Travels and Discoveries in North and Central Africa. Berger, A. Milankovitch theory and climate. Reviews of Geophysics 26 , Broecker, W. Does the trigger for abrupt climate change reside in the ocean or in the atmosphere? Climatic changes of the last 18, years: Observations and model simulations. Science , Abrupt onset and termination of the African Humid Period: Rapid climate responses to gradual insolation forcing.
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Liu, Z. On the cause of abrupt vegetation collapse in North Africa during the Holocene: Climate variability vs. Geophysical Research Letters 33 , L Mercone, D. What set off the aridification in Africa was the replacement of the western arm of the Tethys Sea with the Arabian Peninsula around 7 to 11 million years ago.
The emergence of the Sahara 7 million years ago would have affected the plants and animals in the region—and possibly the early ancestors of human beings. For instance, Sahelanthropus tchadensis , which may be the earliest member in the human family tree , lived just to the south of the Sahara in what is now northern Chad around the time of the transition. Sarah Zielinski is an award-winning science writer and editor.
She is a contributing writer in science for Smithsonian. The Sahara Desert is the world's largest hot desert and the third largest desert behind Antarctica and the Arctic. Located in North Africa, it covers large sections of the continent - covering 9,, square kilometers which is comparable to the are of China or the US!
If you're joining us on our Sahara Desert Trek or just want to find out some interesting facts about the Sahara then keep reading to fuel your wanderlust! The Sahara is the hottest desert in the world — with one of the harshest climates. The area receives little rainfall, in fact, half of the Sahara Desert receives less than 1 inch of rain every year.
Snow falls regularly on several mountain ranges, but nowhere else in the Sahara. The Sahara Desert is the largest hot desert in the world, and the third largest overall after the Antarctica and the Arctic. The Sahara Desert covers an incredible 9. The Sahara is much more than just sand — in fact, the majority of the Sahara is made up of barren, rocky plateaus, as well as salt flats, sand dunes, mountains and dry valleys. The rivers and streams found in the Sahara are all seasonal, apart from the River Nile.
There are over 20 lakes in the Sahara, most of which are saltwater lakes.
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