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Both differential and equatorial heating contributed to African monsoon variations during the mid-Holocene

Adam, Ori and Schneider, Tapio and Enzel, Yehouda and Quade, Jay (2019) Both differential and equatorial heating contributed to African monsoon variations during the mid-Holocene. Earth and Planetary Science Letters, 522 . pp. 20-29. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20190709-091307243

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Abstract

The Sahara was significantly greener 11-5 kya and during multiple earlier interglacial periods. But the mechanisms related to the greening of the Sahara remain uncertain as most climate models severely underestimate past wet conditions over north Africa. The variations in the African monsoon related to the greening of the Sahara are thought to be associated with the variations in the inter-hemispheric differential heating of Earth, caused by orbital variations. However, how orbital variations affect regional climate is not well understood. Using recent theory that relates the position of the tropical rain belt to the atmospheric energy budget, we study the effect of orbital forcing during the mid-Holocene on the African monsoon in simulations provided by the third phase of the Paleo Model Intercomparison Project (PMIP3). We find that energy fluxes in the African sector are related to orbital forcing in a complex manner. Contrary to generally accepted theory, orbital modulation of seasonal differential heating alone is shown to be a weak driver of African monsoon variations. Instead, net atmospheric heating near the equator, which modulates the intensity and extent of seasonal migrations of the tropical rain belt, is an important but overlooked driver of African monsoon variations. A conceptual framework that relates African monsoon variations to both equatorial and inter-hemispheric differential solar heating is presented.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.epsl.2019.06.019DOIArticle
ORCID:
AuthorORCID
Adam, Ori0000-0003-0334-0636
Schneider, Tapio0000-0001-5687-2287
Enzel, Yehouda0000-0001-8367-9255
Additional Information:© 2019 Elsevier B.V. Received 28 January 2019, Revised 15 May 2019, Accepted 17 June 2019, Available online 1 July 2019. The PMIP3 data was downloaded from Earth System Grid Federation (ESGF). Ori Adam acknowledges support by the Israel Science Foundation grant 1185/17.
Funders:
Funding AgencyGrant Number
Israel Science Foundation1185/17
Subject Keywords:PMIP3; African Humid Period; Green Sahara; atmospheric energy budget; energy flux equator; mid-Holocene
Record Number:CaltechAUTHORS:20190709-091307243
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20190709-091307243
Official Citation:Ori Adam, Tapio Schneider, Yehouda Enzel, Jay Quade, Both differential and equatorial heating contributed to African monsoon variations during the mid-Holocene, Earth and Planetary Science Letters, Volume 522, 2019, Pages 20-29, ISSN 0012-821X, https://doi.org/10.1016/j.epsl.2019.06.019. (http://www.sciencedirect.com/science/article/pii/S0012821X19303589)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96944
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:09 Jul 2019 16:58
Last Modified:09 Jul 2019 16:58

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