Nonlinear interactions between the Amazon rainforest and the atmospheric moisture circulation in South America: Possible impacts of ongoing deforestation

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By exchanging large amounts of moisture with the atmosphere through precipitation and evapotranspiration (ET), the Amazonian rainforest strongly influences the low-level atmospheric circulation over South America. This circulation system conveys moisture from the tropical Atlantic ocean to the Amazon basin and farther towards the subtropics. Ongoing deforestation can therefore be assumed to significantly impact the atmospheric moisture content and thus precipitation over large parts of the continent. Using concepts from nonlinear dynamics and complex networks, I intend to model the most relevant coupling mechanisms between the ecosystem and the atmosphere from a conceptual point of view, and to compare the results with corresponding ones obtained using a coupled regional climate model. Special focus would be put on the involved feedback mechanisms: I first plan to quantify the relevance of ET for maintaining the moisture content along the atmospheric transport route. A positive feedback arising from condensation-induced latent heat release over the Amazon basin, and its relevance for maintaining the circulation system, shall then be analysed in detail. This heating leads to an acceleration of the low-level moisture inflow from the adjacent ocean, and should strongly affect the systems sensitivity to changes in the ET rates. After these questions are answered, I intend to investigate how ongoing deforestation of the Amazon rainforest and the resulting decrease in ET will impact the moisture availability downstream of the flow, taking into account the particular sensitivity of the coupling due to the positive feedback. The project would be carried out in three subsequent steps: First, a one-dimensional conceptual model incorporating the geophysical mechanisms relevant for the above three questions would be formulated. Second, I plan to build upon prior work on deriving functional networks from climatological data in order to extend the model to two space dimensions. The equations obtained in the first step shall then be solved along the links of a network representing the main moisture transport routes over South America. Third, results from this conceptual approach shall be compared with corresponding results obtained using a coupled regional climate model.