A deforestation-induced tipping point for the South American monsoon system

Niklas Boers (1) , Norbert Marwan , Henrique M. J. Barbosa , Jürgen Kurths

1 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)

The Amazon rainforest has been proposed as a tipping element of the earth system, with the possibility of a dieback of the entire ecosystem due to deforestation only of parts of the rainforest. Possible physical mechanisms behind such a transition are still subject to ongoing debates. Here, we use a specifically designed model to analyse the nonlinear couplings between the Amazon rainforest and the atmospheric moisture transport from the Atlantic to the South American continent. These couplings are associated with a westward cascade of precipitation and evapotranspiration across the Amazon. We investigate impacts of deforestation on the South American monsoonal circulation with particular focus on a previously neglected positive feedback related to condensational latent heating over the rainforest, which strongly enhances atmospheric moisture inflow from the Atlantic. Our results indicate the existence of a tipping point. In our model setup, crossing the tipping point causes precipitation reductions of up to 40% in non-deforested parts of the western Amazon and regions further downstream. The responsible mechanism is the breakdown of the aforementioned feedback, which occurs when deforestation reduces transpiration to a point where the available atmospheric moisture does not suffice anymore to release the latent heat needed to maintain the feedback.

Domaines: Planète et Univers [physics]; Sciences de la Terre

Niklas Boers, Norbert Marwan, Henrique M. J. Barbosa, Jürgen Kurths. A deforestation-induced tipping point for the South American monsoon system. Scientific Reports, 2017, 7, ⟨10.1038/srep41489⟩. ⟨insu-03727083⟩