Um problema de interação oceano-atmosfera-biosfera: alterações potenciais na vegetação da América do Sul devidas ao aquecimento global

Abstract

One of the expected consequences of global warming is change in the distribution and structure of vegetation. Few studies have evaluated the dynamic behavior of tropical vegetation against a backdrop of elevated CO2, with mixed results for the vegetation in South America. One possibility to explain the opposite results are different patterns of sea surface temperature (SST) used in the simulations. This thesis determines the changes in vegetation structure in South America caused by different climate scenarios for the first half of the 21th century, especially considering the different patterns of SST. In this study were climate experiments using a coupled climate-vegetation model for the A2 IPCC scenario, with ten different patterns of the SST. Initially, it is demonstrated how different predictions for SST for the first half of 21th century increase the uncertainty associated with forecasts of the future distribution of major ecosystems in South America. The increasing uncertainty in the ability to forecast future vegetation patterns is such that by 2050 it is unable to robustly forecast the vegetation cover in an area equivalent to 28% in South America (5 106 km²). The results show that the spatial-temporal variability in SST exerts a strong influence over the vegetation dynamics, there considerable variation in the direction and magnitude of SST effects in different South American regions. However, the simulations for 2011-2050 show that certain patterns of SST are likely to decrease the tropical evergreen rainforest and savanna, and that these areas will be occupied mainly by tropical seasonal rainforest. Thus, the use of different SST patterns in coupled climate-vegetation models is clearly important for improving projections of future vegetation cover in this region.