The greening of the Sahara during the mid-Holocene: results of an interactive atmosphere-biome model

An asynchronously coupled atmosphere biome model was used to assess the biogeophysical interaction during the mid-Holocene, 6000 years before present. The model determines its own land surface conditions and can, therefore, predict quasiequilibrium changes in global vegetation patterns. For the mid-Holocene, the coupled model simulated a northward shift of savanna up to 20 degrees N into the Sahara which in turn amplified the response of the atmospheric circulation to changes in the Earth's orbit during the Holocene. Moreover, in the simulation, most of the western part of the Sahara appeared to be vegetated by xerophytic woods/shrub and warm grass, while the eastern part remained a desert. The simulated vegetation distribution agreed better with palaeobotanical reconstructions than results from the same model, but omitting vegetation-atmosphere interaction.