The biogeochemical cycling of carbon dioxide in the oceans--perturbations by man.

The purpose of the paper is to follow up the contribution by Dyrssen and Turner to the Hemavan meeting in 1993 on CO2 chemistry. Machta's treatment from 1971 of the role of oceans and biosphere in the carbon dioxide cycle is reviewed. Using data on the emission of CO2 and the atmospheric content in addition to the value recently presented by Takahashi et al. for the net sink for global oceans the following numbers have been calculated for the period 1990 to 2000, annual emission of CO2, 6.185 PgC (Petagram = 10(15) g). Annual atmospheric accumulation, 2.930 PgC. Annual sinks, 3.255 PgC. Net uptake for 1990 by the oceans, 1.151 PgC/year. Solubility pump into the mixed layer, 0.828 PgC/year. Residual input (e.g. riverborne), 0.323 PgC/year. Annual uptake by land phytomass, 2.104 PgC. In addition, perturbations involving irrigation and fertilization, limestone dissolution, iron and clathrate addition are mentioned.