It is now well established that the global ocean is on average a CO2 sink of about 2 PgC yr-1 accumulating anthropogenic CO2 with a direct impact on the pH and consequently the marine biota. In recent years, several analyses based on CO2 observations in the North Atlantic, North and Equatorial Pacific, and Southern Ocean, show that the ocean uptake is not steady on interannual to decadal scales and that it might impact the atmospheric CO2 content.