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Astronomically controlled aridity in the Sahara since at least 11 million years ago

Astronomically controlled aridity in the Sahara since at least 11 million years ago
Astronomically controlled aridity in the Sahara since at least 11 million years ago
The Sahara is the largest hot desert on Earth. Yet the timing of its inception and its response to climatic forcing is debated, leading to uncertainty over the causes and consequences of regional aridity. Here we present detailed records of terrestrial inputs from Africa to North Atlantic deep-sea sediments, documenting a long and sustained history of astronomically paced oscillations between a humid and arid Sahara from over 11 million years ago. We show that intervals of strong dust emissions from the heart of the continent predate both the intensification of Northern Hemisphere glaciation and the oldest land-based evidence for a Saharan desert by millions of years. We find no simple long-term gradational transition towards an increasingly arid climate state in northern Africa, suggesting that aridity was not the primary driver of gradual Neogene expansion of African savannah C4 grasslands. Instead, insolation-driven wet–dry shifts in Saharan climate were common over the past 11 Myr, and we identify three distinct stages in the sensitivity of this relationship. Our data provide context for evolutionary outcomes on Africa; for example, we find that astronomically paced arid intervals predate the oldest fossil evidence of hominid bipedalism by at least 4 Myr.
1752-0894
671-676
Crocker, Anya
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Naafs, B. David A.
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Westerhold, Thomas
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James, Rachael
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Cooper, Matthew
54f7bff0-1f8c-4835-8358-71eef8529e7a
Röhl, Ursula
e3029111-f8cc-4bf9-9433-829590c8645d
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1
Xuan, Chuang
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Osborne, Colin P.
89fb6ad9-892c-4120-9f89-cdd6a492beef
Beerling, David J.
2d3b3a81-4c04-4048-8f25-5438bb70fc1e
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Crocker, Anya
1215fbdd-ad43-408a-bd79-c54c6847e68c
Naafs, B. David A.
b4e4a3c0-ef86-476f-a439-3ce7e192337a
Westerhold, Thomas
89fa20ad-d5fc-4f89-9e86-076156510286
James, Rachael
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Cooper, Matthew
54f7bff0-1f8c-4835-8358-71eef8529e7a
Röhl, Ursula
e3029111-f8cc-4bf9-9433-829590c8645d
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1
Xuan, Chuang
3f3cad12-b17b-46ae-957a-b362def5b837
Osborne, Colin P.
89fb6ad9-892c-4120-9f89-cdd6a492beef
Beerling, David J.
2d3b3a81-4c04-4048-8f25-5438bb70fc1e
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6

Crocker, Anya, Naafs, B. David A., Westerhold, Thomas, James, Rachael, Cooper, Matthew, Röhl, Ursula, Pancost, Richard D., Xuan, Chuang, Osborne, Colin P., Beerling, David J. and Wilson, Paul A. (2022) Astronomically controlled aridity in the Sahara since at least 11 million years ago. Nature Geoscience, 15, 671-676. (doi:10.1038/s41561-022-00990-7).

Record type: Article

Abstract

The Sahara is the largest hot desert on Earth. Yet the timing of its inception and its response to climatic forcing is debated, leading to uncertainty over the causes and consequences of regional aridity. Here we present detailed records of terrestrial inputs from Africa to North Atlantic deep-sea sediments, documenting a long and sustained history of astronomically paced oscillations between a humid and arid Sahara from over 11 million years ago. We show that intervals of strong dust emissions from the heart of the continent predate both the intensification of Northern Hemisphere glaciation and the oldest land-based evidence for a Saharan desert by millions of years. We find no simple long-term gradational transition towards an increasingly arid climate state in northern Africa, suggesting that aridity was not the primary driver of gradual Neogene expansion of African savannah C4 grasslands. Instead, insolation-driven wet–dry shifts in Saharan climate were common over the past 11 Myr, and we identify three distinct stages in the sensitivity of this relationship. Our data provide context for evolutionary outcomes on Africa; for example, we find that astronomically paced arid intervals predate the oldest fossil evidence of hominid bipedalism by at least 4 Myr.

Text
Crocker_NatGeo_all_final - Accepted Manuscript
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Published date: 25 July 2022

Identifiers

Local EPrints ID: 469180
URI: http://eprints.soton.ac.uk/id/eprint/469180
ISSN: 1752-0894
PURE UUID: fc9afe2d-96cd-4e08-b022-098264899910
ORCID for Anya Crocker: ORCID iD orcid.org/0000-0001-9561-5750
ORCID for Rachael James: ORCID iD orcid.org/0000-0001-7402-2315
ORCID for Matthew Cooper: ORCID iD orcid.org/0000-0002-2130-2759
ORCID for Chuang Xuan: ORCID iD orcid.org/0000-0003-4043-3073
ORCID for Paul A. Wilson: ORCID iD orcid.org/0000-0001-6425-8906

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Date deposited: 08 Sep 2022 17:08
Last modified: 10 Sep 2022 01:52

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Contributors

Author: Anya Crocker ORCID iD
Author: B. David A. Naafs
Author: Thomas Westerhold
Author: Rachael James ORCID iD
Author: Matthew Cooper ORCID iD
Author: Ursula Röhl
Author: Richard D. Pancost
Author: Chuang Xuan ORCID iD
Author: Colin P. Osborne
Author: David J. Beerling
Author: Paul A. Wilson ORCID iD

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