Enhanced carbon dioxide uptake by the world's oceans

The growth of phytoplankton over much of the ocean is limited by the availability of nitrogen in the upper sunlit region of the ocean. It is through photosynthesis that upper ocean carbon is exported to the deep ocean and replaced with carbon dioxide fluxed by physical processes from the atmosphere. The addition of nitrogen to the ocean surface waters has the potential to recycle the carbon released by burning fossil fuels. It is possible to predict the nitrogen needed by phytoplankton to absorb the carbon dioxide for, say, the IPCC emission scenario B. We have used a Redfield ratio of C:N:P of 130:16:1 and an efficiency of 70%. It is of interest to compare the increase of carbon uptake due to the nitrogen nourishment required for greenhouse gas mitigation with the new primary production of the world's oceans. Not until the year 2100 would the primary production need to be doubled under such a carbon dioxide stabilisation scheme. This is in contrast with terrestrial regions where some modellers estimate that, in order to feed the population increases predicted by the United Nations, the new primary production on land will need to double by 2020. The addition of nitrogen to the upper ocean, as well as sequestering CO2 can be expected to increase the fish landings. If one assumes that the fisheries production rises in proportion to new primary production of the oceans, then each tonne of nitrogen taken up in the upper ocean would increase the fish landings by order 260 Kg.