Global-scale daily riverine DOC fluxes from lands to the oceans with a generic model

Abstract

Abstract The export of riverine dissolved organic carbon (DOC) to the oceans is determinant in carbon exchanges of the estuaries and oceanic food webs. Past research returned a global DOC export around 160–450 TgC.yr−1 by using complex process-based models or yearly average estimates that could have been misjudged. In this study, we try to understand the complex processes explaining daily DOC exports among 341 exoreic watersheds covering 71% of freshwater flows to the oceans. Based on a dataset of DOC concentrations among rivers at the global scale, we were able to link DOC concentrations to daily discharge, the ration between the soil organic carbon content and the amount of precipitations and the average air temperature in the watersheds. We have found a global riverine DOC flux of 131.6 TgC.yr−1 based on daily data and a generic model. Tropical and cold watersheds are the main contributors with 49.5% and 33.3% of the global riverine DOC flux on the two last decades while temperate, semi-arid and polar basins represent 15.9%, 0.7% and 0.6%, respectively. Temporal exports range from 0.1 to 0.16 TgC.day−1 in tropical areas, 0.03–0.32 TgC.day−1 in cold areas and 0.03–0.08 TgC.day−1 in temperate areas. Atlantic and Arctic oceans receive the most important fluxes (0.12–0.2 and 0.01–0.26 TgC.day−1). In a climate change context, this generic equation could be introduced in hydrological modelling tools to predict future DOC fluxes trends.