Global fjords as transitory reservoirs of labile organic carbon modulated by organo-mineral interactions
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The global carbon cycle is strongly modulated by organic carbon (OC) sequestration and decomposition. Whereas the extent of OC sequestration is relatively well-constrained in marine sedimentary basins, there are few quantitative estimates of its susceptibility to decomposition. Fjords are widely distributed hotspots of sedimentation, and currently account for 11% of annual OC burial in marine sediments. Here, we adopt fjords as model systems to investigate the reactivity of sedimentary OC by assessing the distribution of the activation energy (termed E) required to break OC covalent bonds. Our results reveal that OC in fjord sediments is more labile than that in global sediments, which is governed by unique OC provenance and organo-mineral interactions. We estimated that 61±16% of the sedimentary OC in fjords is degradable. Once this OC is remobilized and remineralized during glacial periods (sea level lowstands), the CO2 produced could counterbalance up to 50 ppm of atmospheric CO2 decrease in glacial times, making fjords critical actors in dampening glacial-interglacial climate fluctuations through negative carbon cycling loops.
Cui , X , Mucci , A , Bianchi , T , He , D , Vaughn , D , Williams , E , Wang , C , Smeaton , C , Koziorowska-Makuch , K , Faust , J , Plante , A & Rosenheim , B 2022 , ' Global fjords as transitory reservoirs of labile organic carbon modulated by organo-mineral interactions ' , Science Advances , vol. 8 , no. 46 , eadd0610 . https://doi.org/10.1126/sciadv.add0610
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DescriptionFunding: This work is financially supported by the Shanghai Frontiers Science Center of Polar Science (SCOPS), National Natural Science Foundation of China (NSFC) for Excellent Young Scientists Fund Program (Overseas). J.C.F. has been supported by the European Community’s 7th Framework Programme FP7 2007/2013, Marie-Curie Actions (grant no. 238111).
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