Increase in the uptake rate of oceanic anthropogenic carbon in the North Pacific determined by CFC ages

Abstract

We propose an approach to estimate the rate of increase of oceanic anthropogenic carbon inventory with CFC11 dating technique. This approach relies on the elapsed time from when the water lost contact with atmosphere as determined by CFC age. Furthermore, the assumption is made that it remains constant over a decadal time scale. Finally, we consider only the increase in anthropogenic carbon from one decade to another and not the entire change from the pre-industrial period to the present. The advantages and disadvantages of our approach are discussed. Using this approach, the spatial distributions of the rate of increase of the anthropogenic carbon inventory and the uptake rate of anthropogenic carbon in the North Pacific were obtained. The western North Pacific subtropical region exhibited a maximum in the rate of increase of the anthropogenic carbon inventory of more than 8 g C m −2 year −1 during 1988–1998, which was equivalent to 34% of the total uptake rate in the entire North Pacific. The net total uptake rate of anthropogenic carbon in the whole North Pacific increased with time and was 0.55±0.09 Pg C year −1 during 1988–1998 indicating that the North Pacific absorbs 24% of the whole oceanic uptake of anthropogenic carbon.