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

Ori Adam, Tapio Schneider, Yehouda Enzel, Jay Quade

Research output: Contribution to journalArticle

3 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)20-29
Number of pages10
JournalEarth and Planetary Science Letters
Volume522
DOIs
StatePublished - Sep 15 2019

Keywords

  • African Humid Period
  • atmospheric energy budget
  • energy flux equator
  • Green Sahara
  • mid-Holocene
  • PMIP3

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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