Fig. 3: The importance of river CO2 emission age for the global carbon cycle.
From: Old carbon routed from land to the atmosphere by global river systems
a, Existing model in which river CO2 is only derived from young, rapid-cycling carbon (decadal-aged = green); lateral DIC export to the coast is considered a mixture of decadal and petrogenic inputs (grey). By accounting for these river carbon losses, it is estimated that 1.7 Pg C year−1 of anthropogenic carbon emitted to the atmosphere may be accumulating in the rapid-cycling terrestrial carbon pools3; anote that this estimate is based on a lower estimate of vertical river CO2 emissions of 1.51 Pg C year−1. b, Revised conceptual model based on the assembled F14C values of river DIC, CO2 and CH4 presented here; millennial carbon inputs are needed from organic matter degradation in soils or river sediments (orange) as well as petrogenic carbon from rock weathering to explain the observed F14C values in our database. This revised conceptual model indicates a loss of carbon from an old (millennial) store on land through vertical river CO2 emissions; a first-order estimate of the impact on the partitioning of carbon in the biosphere and soils is provided (b).
