Meridional carbon dioxide transport in the northern North Atlantic

Combination of estimated water transport and accurate measurements of total carbon dioxide (TCO₂) on a hydrographic section at 58 °N allows the assessment of meridional inorganic carbon transport in the northern North Atlantic Ocean. The transport has been decomposed into contributions from the large-scale baroclinic overturning, the Ekman transport, baroclinic and a barotropic eddy terms, and an estimated contribution of the East Greenland Current. These terms are −0.27 · 10⁶, +0.03 · 10⁶, +0.03 · 10⁶, +0.10 · 10⁶, and +0.05 · 10⁶ mol s⁻¹, respectively, which result in a total southward inorganic carbon transport of only −0.06 · 10⁶ mol s⁻¹. An order of magnitude estimate of the meridional transport of dissolved organic carbon (DOC) has shown that in general this term cannot be ignored in the total carbon flux, this being +0.04 · 10⁶ to +0.16 · 10⁶ mol s⁻¹ at 58 °N. A simple carbon budget has been formulated for the temperate North Atlantic, using our flux estimates as well as those of Brewer et al. (1989). This budget shows that the divergence of the meridional carbon flux, connected with the freshwater balance of the ocean may be of the same order of magnitude as the divergence of the total inorganic carbon flux. For an accurate estimate of the total carbon budget of the ocean it will be necessary to take both the DOC transport and the effects of the freshwater balance into account.