Model, proxy and isotopic perspectives on the East African Humid Period

Jessica E. Tierney, Sophie C. Lewis, Benjamin I. Cook, Allegra N. LeGrande, Gavin A. Schmidt

Research output: Contribution to journalArticlepeer-review

106 Scopus citations

Abstract

Both North and East Africa experienced more humid conditions during the early and mid-Holocene epoch (11,000-5000. yr BP; 11-5. ka) relative to today. The North African Humid Period has been a major focus of paleoclimatic study, and represents a response of the hydrological cycle to the increase in boreal summer insolation and associated ocean, atmosphere and land surface feedbacks. Meanwhile, the mechanisms that caused the coeval East African Humid Period are poorly understood. Here, we use results from isotope-enabled coupled climate modeling experiments to investigate the cause of the East African Humid Period. The modeling results are interpreted alongside proxy records of both water balance and the isotopic composition of rainfall. Our simulations show that the orbitally-induced increase in dry season precipitation and the subsequent reduction in precipitation seasonality can explain the East African Humid Period, and this scenario agrees well with regional lake level and pollen paleoclimate data. Changes in zonal moisture flux from both the Atlantic and Indian Ocean account for the simulated increase in precipitation from June through November. Isotopic paleoclimate data and simulated changes in moisture source demonstrate that the western East African Rift Valley in particular experienced more humid conditions due to the influx of Atlantic moisture and enhanced convergence along the Congo Air Boundary. Our study demonstrates that zonal changes in moisture advection are an important determinant of climate variability in the East African region.

Original languageEnglish (US)
Pages (from-to)103-112
Number of pages10
JournalEarth and Planetary Science Letters
Volume307
Issue number1-2
DOIs
StatePublished - Jul 1 2011
Externally publishedYes

Keywords

  • African climate
  • African Humid Period
  • East Africa
  • Holocene climate
  • Hydrogen isotopes
  • Isotope-enabled climate model

ASJC Scopus subject areas

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

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