Variability of Air-Sea CO 2 Fluxes and Dissolved Inorganic Carbon Distribution in the Atlantic Basin: A Coupled Model Analysis

Abstract

The biogeochemical dynamics of carbon in the ocean is a subject of fundamental interest to environmental studies. In this context, we have implemented a ten year run of the Brazilian Earth System Coupled Ocean-Atmosphere Model (BESM-OA2.3) integrated with TOPAZ biogeochemical model for the Atlantic basin. The modeled ΔpCO 2 for the tropical Atlantic shows very clearly a high dominance of positive fluxes, that is, the CO 2 fluxes are sea-to-air through-out the tropical region and for both winter and summer periods. In the mid-latitudes regions negatives fluxes (air-to-sea) were observed for both seasons. An exception to this pattern is an extensive negative tongue on the latitude 10˚N. The occurrence of this negative ΔpCO 2 tongue region in the Tropical Atlantic is highly correlated to negative Evapora-tion-Precipitation values during this season. In the northern hemisphere (NH) summer the negative values of ΔpCO 2 in the tropical Atlantic region are concentrated in the adjacent zone of the Amazon river mouth due to the North Equatorial Counter Current intensification. This process favors the formation of a carbon sink in the adjacent region of the Amazon river mouth. Model results show lowest values of dissolved inorganic carbon (DIC) in a surface layer (100 -150 m). Highest DIC values are observed in deeper layers and concentrated in an equatorial band. The chlorophyll bloom in equatorial zones was well represented by the model. These blooms are the result of equatorial upwelling that brings the high concentration tongues of DIC present in the equatorial band towards the euphotic zone. This is the first published paper about the BESM-OA2.3 integrated with TOPAZ. The presented results suggest that this modeling system is able to reproduce the main regional carbon dynamics features of the mid-latitude/tropical Atlantic.