Biosphere-atmosphere interactions over West Africa. II: Multiple climate equilibria

This paper presents both theoretical and numerical analyses on the multiple -equilibrium nature of the regional climate system in West Africa. Based on simple analyses on how the coupled biosphere-atmosphere system responds to vegetation perturbations within the scope of a dynamic ecosystem, we propo se that the regional climate system may have multiple equilibrium states co existing under the same precessional forcing. Using a synchronously coupled biosphere-atmosphere model which includes explicit representation of ecosy stem dynamics, we show that the equilibrium state of the model is sensitive to initial vegetation distribution. This modelling result supports the exi stence of multiple climate equilibria. Using the same model, further experi ments are carried out to investigate how the coupled system responds to non -permanent vegetation perturbations. Our results demonstrate how transition s between different climate equilibria can take place when governed by the two-way biosphere-atmosphere feedback. These findings advance our understan ding regarding the mechanisms of climate variability over West Africa.