Résumé
Measured concentrations of CO 2 , O 2 , and related chemical species in a section across the Florida Straits and in the open Atlantic Ocean at approximately 25°N, have been combined with estimates of oceanic mass transport to estimate both the gross transport of CO 2 by the ocean at this latitude and the net CO 2 flux from exchange with the atmosphere. The northward flux was 63.9 × 10 6 moles per second (mol/s); the southward flux was 64.6 × 10 6 mol/s. These values yield a net CO 2 flux of 0.7 × 10 6 mol/s (0.26 ± 0.03 gigaton of C per year) southward. The North Atlantic Ocean has been considered to be a strong sink for atmospheric CO 2 , yet these results show that the net flux in 1988 across 25°N was small. For O 2 the equivalent signal is 4.89 × 10 6 mol/s northward and 6.97 × 10 6 mol/s southward, and the net transport is 2.08 × 10 6 mol/s or three times the net CO 2 flux. These data suggest that the North Atlantic Ocean is today a relatively small sink for atmospheric CO 2 , in spite of its large heat loss, but a larger sink for O 2 because of the additive effects of chemical and thermal pumping on the CO 2 cycle but their near equal and opposite effects on the CO 2 cycle.