Modeling Variability in Vertical Profiles of Particulate Organic Carbon Flux

Abstract The vertical flux of particulate organic carbon (POC) from the surface to the deep ocean regulates the ocean carbon uptake, with implications for the Earth's carbon cycle. It is debated in the literature what functional form best describes the attenuation of this flux with depth. The wide scatter found in measurements of the flux has impeded progress on this question. A theoretical model is proposed, which treats this scatter as key information rather than noise. Based on the evidence that the POC flux data follow a lognormal distribution, the model predicts the vertical POC flux profile as a function of three parameters: log‐mean and log‐standard deviation of the POC export flux, and a depth scaling term consistent with previous functional forms. The model captures the large variability observed in individual POC flux profiles and illustrates that large POC flux events contribute substantially to the vertical transfer of POC.