Global patterns of particulate organic carbon export from land to the ocean

Abstract

Global rivers and streams are important carbon transport pathways from land to the ocean. However, few studies have quantified terrigenous carbon dynamics in river ecosystems and its variations due to climate change and anthropogenic perturbations. Therefore, our study analysed fluvial particulate organic carbon (POC) and developed a processed-based model (TRIPLEX-HYDRA) to simulate the production, transport and removal (i.e., deposition, degradation and dam retention) processes of fluvial POC along the land-ocean aquatic continuum (LOAC). Based on our results, approximately 0.29 Pg of POC is exported from land to the ocean through rivers each year. More specifically, we found that rivers at low latitudes (30 S-30 N, 0.18 Pg yr À1 ) and high northern latitudes (60 N-90 N, 0.05 Pg yr À1 ) had higher POC fluxes compared to rivers in other regions. This high POC flux is related to strong erosion rates and high soil organic carbon storage. Additionally, our model simulation revealed that total POC flux from global river has not significantly changed from 1983 to 2015 but displays markedly decreased or increased trend at regional scale.

The Global Turbidity Current Pump and Its Implications for Organic Carbon Cycling

“…This led to an estimated burial flux of terrestrial OC in marine sediments of ∼40-80 Mt/year (Burdige 2005 West 2020) (Table 1). Rivers are estimated to supply ∼200-300 Mt/year of terrestrial OC to the oceans (Galy et al 2015, Hilton & West 2020, Li et al 2022) (Table 1). This produces estimates of global burial efficiency for terrestrial OC in marine sediments of ∼13-40% (Table 1; Supplemental Material).…”

“…A second method uses the abundance of terrestrial OC and sediment accumulation rates measured in seabed sediment cores together with representative areas to calculate burial fluxes (Smith et al 2015;Cartapanis et al 2016Cartapanis et al , 2018Rabouille et al 2019;Baudin et al 2020;Li et al 2022). Although this method is currently not feasible due to spatially limited OC measurements in cores from turbidite systems, it holds promise for future estimates of terrestrial OC burial in submarine fans by extending published core data for submarine fan accumulation rates (e.g., Covault & Graham 2010) to include TOC and terrestrial OC fractions.…”

“…Although this method is currently not feasible due to spatially limited OC measurements in cores from turbidite systems, it holds promise for future estimates of terrestrial OC burial in submarine fans by extending published core data for submarine fan accumulation rates (e.g., Covault & Graham 2010) to include TOC and terrestrial OC fractions. It should also be noted that cores from submarine fans may be significantly underrepresented in global core databases previously used for TOC burial estimates in marine sediments (Cartapanis et al 2016(Cartapanis et al , 2018Li et al 2022). Furthermore, sandy seabed areas are often impractical to core via traditional piston or gravity corers, potentially leading to other biases.…”

“…This raises the question of how highly variable burial flux of OC in marine sediment affects global carbon cycling and atmospheric pCO 2 levels, and thus climate (Cartapanis et al 2016, 2018, Li et al 2022. Burial of OC in marine sediment affects atmospheric CO 2 levels only over long timescales (>1,000 years) (Galy et al 2007, Blair & Aller 2012, Hilton & West 2020.…”

“…(b) Global OC mass fluxes (in green). Values are from h Burdige (2005), i Burdige (2007), j Hilton & West (2020), l Cartapanis et al (2018), m Li et al (2022), n Galy et al (2015), o Wadham et al (2019), p Gaillardet et al (1999), q Plank & Manning (2019), and r this review. This diagram summarizes global pathways of both terrestrial (black) and marine (blue) OC.…”