Articles | Volume 12, issue 19
Biogeosciences, 12, 5793–5809, 2015
Biogeosciences, 12, 5793–5809, 2015

Research article 12 Oct 2015

Research article | 12 Oct 2015

Air-sea CO2 fluxes and the controls on ocean surface pCO2 seasonal variability in the coastal and open-ocean southwestern Atlantic Ocean: a modeling study

R. Arruda1, P. H. R. Calil1, A. A. Bianchi2,3, S. C. Doney4, N. Gruber5, I. Lima4, and G. Turi5,a R. Arruda et al.
  • 1Laboratório de Dinâmica e Modelagem Oceânica (DinaMO), Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, RS, Brazil
  • 2Departamento de Ciencias de la Atmósfera y los Oceános, Universidad de Buenos Aires, Buenos Aires, Argentina
  • 3Departamento Oceanografía, Servicio de Hidrografía Naval, Av. Montes de OCA2124-Buenos Aires, Argentina
  • 4Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
  • 5Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland
  • anow at: CIRES, University of Colorado at Boulder, and NOAA/ESRL, Boulder, CO, USA

Abstract. We use an eddy-resolving, regional ocean biogeochemical model to investigate the main variables and processes responsible for the climatological spatio-temporal variability of pCO2 and the air-sea CO2 fluxes in the southwestern Atlantic Ocean. Overall, the region acts as a sink of atmospheric CO2 south of 30° S, and is close to equilibrium with the atmospheric CO2 to the north. On the shelves, the ocean acts as a weak source of CO2, except for the mid/outer shelves of Patagonia, which act as sinks. In contrast, the inner shelves and the low latitude open ocean of the southwestern Atlantic represent source regions. Observed nearshore-to-offshore and meridional pCO2 gradients are well represented by our simulation. A sensitivity analysis shows the importance of the counteracting effects of temperature and dissolved inorganic carbon (DIC) in controlling the seasonal variability of pCO2. Biological production and solubility are the main processes regulating pCO2, with biological production being particularly important on the shelves. The role of mixing/stratification in modulating DIC, and therefore surface pCO2, is shown in a vertical profile at the location of the Ocean Observatories Initiative (OOI) site in the Argentine Basin (42° S, 42° W).

Short summary
We investigate surface ocean pCO2 and air-sea CO2 fluxes climatological variability through biogeochemical modeling in the southwestern Atlantic Ocean. Surface ocean pCO2 spatio-temporal variability was found to be controlled mainly by temperature and Dissolved Inorganic Carbon (DIC). Biological production, physical transport and solubility are the main controlling processes. With different behaviors on subtropical and subantarctic open ocean, and on inner/outer continental shelves.
Final-revised paper