The impacts of Amazon deforestation on climate change are investigated through the use of twin numerical experiments with an Atmospheric General Circulation Model (AGCM) with prescribed global sea surface temperature and the same AGCM coupled to an ocean GCM over the global-tropics (CGCM).An ensemble approach is adopted, with ten member ensemble-averages of a control simulation compared with perturbed simulations for three scenarios of Amazon deforestation. The latest 20 years of simulation from each experiment are analyzed. Local surface warming and rainfall reduction are simulated by both models over the Amazon basin, with the coupled model presenting rainfall reduction that is nearly 60% larger compared to its control run than those obtained by the AGCM. The results also indicated that both the fraction of the deforested area and the spatial continuity of vegetated area might be important for modulating global climate variability and change. Additionally, significant remote atmospheric responses to Amazon deforestation scenarios are detectable for the coupled simulations, which revealed global ocean and atmosphere circulation changes conducive to enhanced ocean-atmosphere variability over the Pacific Ocean. This, in turn, is interpreted as a manifestation of enhanced El Niño-Southern Oscillation (ENSO) activity over the Pacific and a positive feedback contributing to the extra rainfall reduction over the Amazon on the coupled simulations.

[1] The western Equatorial Undercurrent (EUC) and North Equatorial Countercurrent (NECC) are investigated at 38°W using contemporaneous subsurface (ADCP) and high-resolution near-surface (drifters + satellite altimeter) velocity measurements, together with hydrographic (CTDO 2 ) data that were collected from 1998 to 2006. The observations reveal an EUC with a strong semiannual pattern of intensification. Direct measurements also confirm the existence of a northern branch of the NECC (nNECC), observed here for the first time in the western tropical Atlantic. The NECC displays an annual cycle of northward migration on the basin, driven by the Sverdrup transport generated by the wind field. In this cycle the nNECC is a semipersistent feature fed by waters from the Northern Hemisphere and the residual nNECC flow from the previous year.

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The fugacity of CO 2 (fCO 2 ) has been measured underway during three quasi-synoptic cruises in the western tropical Atlantic in