Control of air‐sea CO₂ disequilibria in the subtropical NE Atlantic by planktonic metabolism under the ocean skin

Abstract

The air‐sea CO 2 gradient at the subtropical NE Atlantic was strongly dependent on the metabolism of the planktonic community within the top cms, but independent of that of the communities deeper in the water column. Gross primary production (GPP) and community respiration (R) of the planktonic community within the top cms exceeded those of the communities deeper in the water column by >10‐fold and >7 fold, respectively. Net autotrophic metabolism (GPP > R) at the top cms of the water column in some stations drove CO 2 uptake by creating a CO 2 deficit at the ocean surface, while net heterotrophic metabolism (GPP < R) at the top cms of the water column in other stations resulted in strong CO 2 supersaturation, driving CO 2 emissions. These results suggest a strong control of the air‐sea p CO 2 anomaly by intense biological processes.