Global riverine land-to-ocean carbon export constrained by observations and multi-model assessment
2024
Liu, Maodian | Raymond, Peter | Lauerwald, Ronny | Zhang, Qianru | Trapp-Müller, Gerrit | Davis, Kay | Moosdorf, Nils | Xiao, Changhao | Middelburg, Jack | Bouwman, Alexander | Beusen, Arthur | Peng, Changhui | Lacroix, Fabrice | Tian, Hanqin | Wang, Junjie | Li, Mingxu | Zhu, Qiuan | Cohen, Sagy | van Hoek, Wim | Li, Ya | Li, Yangmingkai | Yao, Yuanzhi | Regnier, Pierre | Peking University [Beijing] | Yale School of the Environment (YSE) | Université Paris-Saclay | Ecologie fonctionnelle et écotoxicologie des agroécosystèmes (ECOSYS) ; AgroParisTech-Université Paris-Saclay-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | Nicholas School of the Environment ; Duke University [Durham] | Key Laboratory for Earth Surface Processes of the Ministry of Education ; Peking University [Beijing] | Universiteit Utrecht / Utrecht University [Utrecht] | Australian Institute of Marine Science (AIMS) | Leibniz Centre for Tropical Marine Research (ZMT) | Christian-Albrechts-Universität zu Kiel = Christian-Albrechts University of Kiel = Université Christian-Albrechts de Kiel (CAU) | PBL Netherlands Environmental Assessment Agency | Hunan Normal University (HNU) | Université du Québec à Montréal = University of Québec in Montréal (UQAM) | Universität Bern = University of Bern = Université de Berne (UNIBE) | Oeschger Centre for Climate Change Research (OCCR) ; Universität Bern = University of Bern = Université de Berne (UNIBE) | Boston College (BC) | Institute of geographical sciences and natural resources research [CAS] (IGSNRR) ; Chinese Academy of Sciences [Beijing] (CAS) | Hohai University | University of Alabama [Tuscaloosa] (UA) | Research Center for Eco-Environmental Sciences (RCEES) ; Chinese Academy of Sciences [Changchun Branch] (CAS) | East China Normal University [Shangaï] (ECNU) | Université libre de Bruxelles (ULB)
International audience
Show more [+] Less [-]English. Rivers are a key component of the global carbon cycle. They receive vast quantities of terrestrial carbon, of which a large fraction is ultimately exported to the coastal ocean. Our review of previously published assessments reveals that substantial uncertainties remain with regard to the spatial distribution and speciation of the carbon export. Accurate quantification of the relative contributions of dissolved, particulate, organic and inorganic carbon to the total amounts is, however, of crucial importance for the coupling between the terrestrial and marine carbon cycles. Breaking down existing spatially explicit assessments over large river basins, we find a disagreement in flux estimates that exceeds two orders of magnitude for more than half of the basins. Using machine-learning techniques in combination with a multi-model ensemble and an updated database of observations, we overcome the inconsistencies in existing assessments and narrow down uncertainties in riverine carbon exports. Our revised assessment yields a global riverine export of 1.02 ± 0.22 (2σ) PgC yr−1. This carbon flux is partitioned into 0.52 ± 0.17, 0.30 ± 0.14, 0.18 ± 0.04 and 0.03 ± 0.02 PgC yr−1 of dissolved inorganic, dissolved organic, particulate organic and particulate inorganic carbon, respectively. We estimate the carbon contribution through groundwater export to be minor (0.016 PgC yr−1). Our assessment suggests an underestimation of the land-to-ocean carbon flux by 0.24 PgC yr−1 by the Intergovernmental Panel on Climate Change (IPCC) and calls for a revision of the oceanic carbon budget.
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