Articles | Volume 11, issue 2
Clim. Past, 11, 175–185, 2015

Special issue: Integrated analysis of interglacial climate dynamics

Clim. Past, 11, 175–185, 2015

Research article 06 Feb 2015

Research article | 06 Feb 2015

North African vegetation–precipitation feedback in early and mid-Holocene climate simulations with CCSM3-DGVM

R. Rachmayani1, M. Prange1,2, and M. Schulz1,2 R. Rachmayani et al.
  • 1Faculty of Geosciences, University of Bremen, Klagenfurter Strasse, 28334 Bremen, Germany
  • 2MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, 28359 Bremen, Germany

Abstract. The present study analyses the sign, strength, and working mechanism of the vegetation–precipitation feedback over North Africa in middle (6 ka BP) and early Holocene (9 ka BP) simulations using the comprehensive coupled climate–vegetation model CCSM3-DGVM (Community Climate System Model version 3 and a dynamic global vegetation model). The coupled model simulates enhanced summer rainfall and a northward migration of the West African monsoon trough along with an expansion of the vegetation cover for the early and middle Holocene compared to the pre-industrial period. It is shown that dynamic vegetation enhances the orbitally triggered summer precipitation anomaly by approximately 20% in the Sahara–Sahel region (10–25° N, 20° W–30° E) in both the early and mid-Holocene experiments compared to their fixed-vegetation counterparts. The primary vegetation–rainfall feedback identified here operates through surface latent heat flux anomalies by canopy evaporation and transpiration and their effect on the mid-tropospheric African easterly jet, whereas the effects of vegetation changes on surface albedo and local water recycling play a negligible role. Even though CCSM3-DGVM simulates a positive vegetation–precipitation feedback in the North African region, this feedback is not strong enough to produce multiple equilibrium climate-ecosystem states on a regional scale.

Short summary
The role of vegetation-precipitation feedbacks in modifying the North African rainfall response to enhanced early to mid-Holocene summer insolation is analysed using the climate-vegetation model CCSM3-DGVM. Dynamic vegetation amplifies the positive early to mid-Holocene summer precipitation anomaly by ca. 20% in the Sahara-Sahel region. The primary vegetation feedback operates through surface latent heat flux anomalies by canopy evapotranspiration and their effect on the African easterly jet.