Comparative Analysis of Brazil Current System Oceanic Transports in Four IPCC AR4 Climate Models

Much about the dynamics and variability of oceanographic parameters in interannual scales for the South Atlantic Ocean is still unknown, particularly what concerns the sensibility of South Atlantic and of its currents in relation to the climate change scenarios. Hence the aim of this work is to investigate the behavior of volume transport and heat flux patterns which are related to the Brazil Current System (BCS) according to the climate change scenarios suggested by the Intergovernmental Panel on Climate Changes (IPCC) through the comparative analysis between data deriving from the four IPCC Fourth Assessment Report (AR4) global climate models. This kind of study can contribute to the increase of oceanographic knowledge concerning climate change scenarios as well as to the evaluation of prognostic fields generated from several different global models which can be used in the regional oceanic downscaling. The results deriving from GFDL-CM2.1, UKMO-HadCM3, CCSM3 and MIROC3.2(Hires) models for the future scenario of climate change B1 (“optimistic” scenario characterized by carbon dioxide stabilized in 550 ppm) and for the scenario that represents the climate in the Twentieth Century (20C3M) have been used in this work. The volume transport and heat flux integrated for the whole BCS and for each water mass which constitutes the system (Tropical Water - TW, South Atlantic Central Water - SACW and Antarctic Intermediate Water - AAIW) have been calculated employing these data. Estimates were made for three zonal sections (at 23° S, 25° S and 30° S) and then were used in the Wavelet Analysis aimed at identifying the temporal variability patterns of BCS series of volume transport and heat flux. This analysis made it possible to determine the annual average volume transport for the year corresponding to the highest energy of series of volume transports integrated in B1, which were compared to the average transports of 20C3M afterwards. The performed analysis showed the occurrence of interannual variability for the estimated properties which are connected with the climate scenario B1. It also showed that the BCS shows changes in both intensity and variability of these parameters when compared to B1. Comparison between the results deriving from the four models for a same scenario indicates significant differences in the BCS vertical structure representation of the examined sections and in the associated oceanic transports as well as in the temporal variability of the analyzed parameters.