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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 14, issue 7
Clim. Past, 14, 1051-1066, 2018
https://doi.org/10.5194/cp-14-1051-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Clim. Past, 14, 1051-1066, 2018
https://doi.org/10.5194/cp-14-1051-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 12 Jul 2018

Research article | 12 Jul 2018

Rapid increase in simulated North Atlantic dust deposition due to fast change of northwest African landscape during the Holocene

Sabine Egerer1,2, Martin Claussen1,3, and Christian Reick1 Sabine Egerer et al.
  • 1Max Planck Institute for Meteorology, Bundesstraße 53, 20146 Hamburg, Germany
  • 2International Max Planck Research School on Earth System Modelling, Bundesstraße 53, 20146 Hamburg, Germany
  • 3Center for Earth System Research and Sustainability, Universität Hamburg, Bundesstraße 53, 20146 Hamburg, Germany

Abstract. Marine sediment records from a series of core sites along the northwest African margin show a sudden increase in North Atlantic dust deposition at about 5kaBP that has been associated with an abrupt end of the African Humid Period (AHP). To assess the causes of the abrupt shift in North Atlantic dust deposition, we explore changes in the Holocene dust cycle and in North African climate and landscape by performing several time slice simulations from 8kaBP until the preindustrial era. To do this, we use the coupled aerosol–climate model ECHAM6–HAM2 including dynamic vegetation and interactive dust, wherein ocean conditions and lake surface area are prescribed for each time slice.

We find a rapid increase in simulated dust deposition between 6 and 4kaBP that is fairly consistent with the abrupt change in marine sediment records at around 20°N close to the northwest African margin. At more northern and more remote cores, a significant change in dust deposition is noticeable roughly between 6 and 2kaBP in the simulations as well as in the records, but the change is less sharp compared to the near-margin core sites. The rapid change in simulated dust deposition is caused by a rapid increase in simulated dust emissions in the western Sahara, where the main dust sources for dust transport towards the North Atlantic are located. The sudden increase in dust emissions in the western Sahara is according to our simulations a consequence of a fast decline of vegetation cover from 22 to 18°N that might occur due to vegetation–climate feedbacks or due to the existence of a precipitation threshold on vegetation growth. Additionally, the prescribed gradual reduction of lake area enforces accelerated dust release as highly productive dust sources are uncovered. Concurrently with the continental drying, surface winds in the western Sahara are accelerated. Changes in the Saharan landscape and dust emissions south of 18°N and in the eastern Sahara play a minor role in driving the dynamics of North Atlantic dust deposition at the core sites. Our study identifies spatial and temporal heterogeneity in the transition of the North African landscape. As a consequence, implications from local data records on large-scale climate have to be treated with caution.

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We find a rapid increase in simulated dust deposition between 6 and 4 ka BP that is fairly consistent with an abrupt change in dust deposition that was observed in marine sediment records at around 5 ka BP. This rapid change is caused by a rapid increase in simulated dust emissions in the western Sahara due to a fast decline in vegetation cover and a locally strong reduction of lake area. Our study identifies spatial and temporal heterogeneity in the transition of the North African landscape.
We find a rapid increase in simulated dust deposition between 6 and 4 ka BP that is fairly...
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