How is particulate organic carbon transported through the river-fed Congo Submarine Canyon to the deep-sea?
Type | Article | ||||||||
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Acceptance Date | 2024-04-04 IN PRESS | ||||||||
Language | English | ||||||||
Author(s) | Hage Sophie9, Baker Megan L.2, Babonneau Nathalie9, Soulet Guillaume1, Dennielou Bernard1, Silva Jacinto Ricardo1, Hilton Robert G.3, Galy Valier4, Baudin François5, Rabouille Christophe6, Vic Clement7, Sahin Sefa8, Açikalin Sanem8, Talling Peter J.2 | ||||||||
Affiliation(s) | 1 : Geo-Ocean, UMR6538, Univ Brest, Ifremer, CNRS, Plouzané, France 2 : Departments of Geography and Earth Sciences, Durham University, UK 3 : Department of Earth Sciences, University of Oxford, UK 4 : Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MA, USA 5 : ISTeP, UMR 7193, Sorbonne Université, CNRS, Paris, France 6 : LSCE, UMR 8212, CEA-CNRS-UVSQ, IPSL and Université Paris-Saclay, Gif-sur-Yvette, France 7 : Univ Brest, CNRS, Ifremer, IRD, Laboratoire d’Océanographie Physique et Spatiale (LOPS), IUEM, Plouzané, France 8 : School of Natural and Environmental Sciences, Newcastle University, UK 9 : Geo-Ocean, UMR6538, Univ Brest, Ifremer, CNRS, Plouzané, France |
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Source | EGUSphere (Copernicus GmbH) In Press | ||||||||
DOI | 10.5194/egusphere-2024-900 | ||||||||
Note | This preprint is open for discussion. | ||||||||
Abstract | The transfer of carbon from land to the near-coastal ocean is increasingly being recognized in global carbon budgets. However, a more direct transfer of terrestrial carbon to the deep-sea is comparatively overlooked. Among systems that connect coastal to deep-sea environments, the Congo Submarine Canyon is of particular interest since the canyon head starts 30 km into the Congo River estuary, which delivers ~7 % of the total organic carbon from the world’s rivers. However, carbon and sediment transport mechanisms that operate in the Congo Canyon, and submarine canyons more globally, are poorly constrained compared to rivers because monitoring of deep-sea canyons remains challenging. Using a novel array of acoustic instruments, sediment traps and cores, this study seeks to understand the hydrodynamic processes that control delivery of particulate organic carbon via the Congo Submarine Canyon to the deep-sea. We show that particulate organic carbon transport in the canyon-axis is modulated by two processes. First, we observe periods where the canyon dynamics are dominated by tides, which induce a background oscillatory flow (speeds of up to 0.15 m/s) through the water column, keeping muds in suspension, with a net upslope transport direction. Second, fast-moving (up to 8 m/s) turbidity currents occur for 35 % of the time during monitoring periods and transport both muddy and sandy particulate organic carbon at an estimated transit flux that is more than ten times the flux induced by tides. Remarkably, organic carbon transported and deposited in the submarine canyon has a similar isotopic composition to organic carbon in the Congo River, and in the deep-sea fan at 5 km of water depth. Episodic turbidity currents, together with background tidal currents thus promote efficient transfer of river-derived particulate organic carbon in the Congo Submarine Fan, leading to some of the highest terrestrial carbon preservation rates observed in marine sediments globally. |
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