A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

Amazonian forest die-back in the Hadley Centre coupled climate-vegetationmodelRichard A. Betts*, Peter M. Cox*, Matthew Collins † , John H. C. Gash ‡ , Philip P.Harris ‡ , Chris Huntingford ‡ , Chris D. Jones* and Keith D. Williams**Hadley Centre, Met Office, UK† Department of Meteorology, Reading University, UK‡ Centre for Ecology and Hydrology, UKThe Hadley Centre General Circulation Model HadCM3 simulates severeprecipitation reductions over a large part of the Amazon region as a consequence ofincreasing greenhouse gas concentrations. In a version of HadCM3 incorporating theTRIFFID dynamic global vegetation model, this drying leads to a major loss of forestcover. The simulated Amazonian ecosystems therefore undergo radical changes incharacter, and the region becomes a significant source of CO 2 . Consequently, theregional-scale climate and ecosystem changes in Amazonia provide a positivefeedback on global warming.The mechanisms of drying and die-back are complex and involve a number offeedbacks between CO 2 concentration, the atmospheric circulation, sea surfacetemperatures, surface hydrology and vegetation. This paper presents currentunderstanding of the simulated climate and vegetation changes, and discussesinvestigations into the robustness of the model result.Richard A. BettsMet OfficeHadley Centre for Climate Prediction and ResearchLondon RoadBracknellBerkshireRG12 2SYUKTel: +44 1344 856877Fax: +44 1344 854898Email: richard.betts@metoffice.com