Avaliação da representação de massas d’água pelos modelos do CMIP5 e CMIP6 durante o período histórico e projeções futuras na região da Corrente do Brasil ao longo da radial de monitoramento de alta densidade de XBT NOAA AX97

Abstract

This study evaluates the ability of Earth System Models (ESMs) and Atmosphere-Ocean General Circulation Models (AOGCM) from the CMIP5 and CMIP6 phases to represent the thermohaline structure and ocean circulation in the Brazil Current (BC) region, with emphasis on the analysis of water masses along the high-density NOAA-AX97 XBT transect. In situ observational data from the MOVAR project, the ORAS5 ocean reanalysis, and ESM/AOGCM simulations were used. The analysis covered both the historical period (1976–2005) and future projections (2041–2070 and 2071–2100), focusing on different CMIP6 scenarios (SSP1–2.6, SSP2–4.5, and SSP5–8.5). The results show that the GFDL-CM4 model (CMIP6), with higher spatial resolution, performs best in representing the BC and its associated water masses, particularly in the surface and intermediate layers. It was observed that the quality of the representation depends more on the model’s resolution than on the CMIP phase. Regarding future projections, no clear trend of increase or decrease in volume or heat transport was identified across scenarios, indicating high uncertainty in regional outcomes. The research highlights the importance of continuous observational efforts, such as MOVAR, and the careful selection of models in regional studies, aiming for a better understanding of the South Atlantic Ocean's response to climate change.