Burning of fossil fuels and deforestation annually puts slightly over 6 Pg (1Pg = 105 g) of carbon as CO2 into the atmosphere. But only about 3 Pg of this CO2 remains in the atmosphere, the rest being taken up by the ocean and the terrestrial biosphere (Quay, 2002). The North Atlantic Ocean is likely the largest ocean sink for atmospheric CO2 in the Northern Hemisphere, but its variability from year to year is very large. This variability, according to Gruber et al (2002) is largely due to variations in winter mixed-layer depths and by sea-surface temperature fluctuation. These basin-wide variations are associated with basin-wide temperature variations known as the North Atlantic Oscillation (NAO). The annual change in the North Atlantic carbon sink is about ± 0.3 Pg of carbon, which is about 50% of the annual uptake.
References
Gruber, N., C. D. Keeling, and N. R. Bates, 2002: Interannual variability in the North Atlantic Ocean carbon sink. Science, 298, 2374-2378.
Quay, P., 2002: Ups and downs of CO2 uptake. Science, 298, 2344