EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Green Sahara Megaperiods during the Pliocene: What was the role of North Atlantic Ocean temperature?

Paul Wilson1, Amy Jewell1, Anya Crocker1, Solana Buchanan2, Bryce Mitsunaga3, Thomas Westerhold4, Ursula Röhl4, James Russell3, and Timothy Herbert3
Paul Wilson et al.
  • 1University of Southampton, National Oceanography Centre Southampton, Ocean and Earth Science, United Kingdom of Great Britain and Northern Ireland (
  • 2Rice University, Department of Chemistry, Houston, TX, United States
  • 3Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island USA
  • 4MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, 28359 Bremen, Germany

The Sahel region is one of the most vulnerable regions on Earth to anthropogenically-driven climate change, but also one of the least equipped to deal with the consequences. Predictions of precipitation levels over the forthcoming centuries diverge, not only in magnitude, but also in the sign of change. One key aspect of this uncertainty comes from the role of Atlantic Ocean sea surface temperatures (SST), which are known to exert a strong control over precipitation in the Sahel and are implicated in both the major drought of the late 20th century and extreme droughts associated with the Heinrich events of the last glacial. To better understand how Sahelian hydroclimate may respond to SST variability in a warmer world, we turn to the Pliocene epoch, when atmospheric CO2 levels were comparable to present.


We studied sediments from Ocean Drilling Project Site 659, which is situated in the subtropical North Atlantic beneath the major modern summer Saharan dust plume. Our new dust accumulation rates and X-ray fluorescence core scan data indicate that there were major shifts between highly arid conditions and humid intervals with vegetated or “Green Sahara” conditions over much of northern Africa, driven by both solar insolation and glacial-interglacial variability. We also report three unusually long Plio-Pliocene humid intervals (each lasting ca. 100 kyr) characterised by very low dust emissions, that we term “Green Sahara Megaperiods (GSMPs)”. All three of these GSMPs occur at times when insolation variability was weak, resulting in values close to the long-term mean. This observation strongly suggests that factors other than insolation drove the sustained humidity of GSMPs. We present paired alkenone SST estimates and multi-species planktonic foramaniferal isotope records from 3.5–2.3 Myr ago to explore the extent to which the GSMPs were accompanied by intervals of extended warmth in the surface waters of the North Atlantic Ocean.

How to cite: Wilson, P., Jewell, A., Crocker, A., Buchanan, S., Mitsunaga, B., Westerhold, T., Röhl, U., Russell, J., and Herbert, T.: Green Sahara Megaperiods during the Pliocene: What was the role of North Atlantic Ocean temperature?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20327,, 2020