Numerical study of the impact of greenhouse gases on the South Atlantic Ocean climatology

The National Center for Atmospheric Research Community Climate System Model (NCAR CCSM, version 3) numerical coupled model is used to understand the climatic impacts on the South Atlantic Ocean due to industrialization and consequent increase of greenhouse gas emission. Two experiments are analyzed: the first one with trace/greenhouse gases at pre-industrial levels and a second one where present day levels were adopted. The results show that the annual averaged sea surface temperature, sea level pressure and barotropic transport intensify and precipitation weakens from one period to the next. With respect to the seasonal cycle, the sea surface temperature warms relative to the pre-industrial period mainly during the winter and spring; while sea level pressure presents higher values in summer and autumn. Barotropic transport has revealed significant differences between the two experiments at middle and high latitudes. Increased transport is associated with the intensification of the Subtropical Gyre and the Antarctic Circumpolar Current. Changes in barotropic transport and sea surface temperature leads to an intensification of the Polar Front and associated gradients. Examination of the precipitation field differences showed an increase over the Amazon region and along the South Atlantic Convergence Zone, during summer. The changes in sea surface temperature, sea-level pressure and barotropic transport from the pre-industrial period to the present day were more pronounced at high latitudes. These reach almost 1 degreesC and 11Sv between 45-60degrees S, respectively. Major differences in precipitation are confined to the tropics.