PREDICTING THE OCEANIC INPUT OF ORGANIC-CARBON BY CONTINENTAL EROSION

For a large set of major world rivers we established the empirical rel ations existing between the observed organic carbon fluxes and the cli matic, biologic, and geomorphologic patterns characterizing the river basins. These characteristics were extracted from various ecological d atabases. The corresponding carbon fluxes were taken from the literatu re. Dissolved organic carbon fluxes are mainly related to drainage int ensity, basin slope, and the amount of carbon stored in soils. Particu late organic carbon fluxes are calculated as a function of sediment fl uxes, which depend principally upon drainage intensity, rainfall inten sity, and basin slope. Although the drainage intensity is mainly relat ed to the amount of precipitation and to mean temperature in the basin , slope is also retained as one of the controlling factors. Our empiri cal models result in a total organic carbon flux to the oceans of abou t 0.38 Gt per year globally. About 0.21 Gt carbon (Gt C) enter the oce ans in dissolved form and about 0.17 Gt C in particulate form, We furt her regionalize fluxes with respect to major climates, different conti nents, and different ocean basins. About 45% of the organic carbon is discharged from tropical wet regions. The major part of the dissolved organic carbon is discharged into the Atlantic Ocean, while the bulk o f the particulate organic carbon is discharged into the Indian and Pac ific Oceans.