Longest sediment flows yet measured show how major rivers connect efficiently to deep sea

Here we show how major rivers can efficiently connect to the deep-sea, by analysing the longest runout sediment flows (of any type) yet measured in action on Earth. These seafloor turbidity currents originated from the Congo River-mouth, with one flow travelling >1,130 km whilst accelerating from 5.2 to 8.0 m/s. In one year, these turbidity currents eroded 1,338-2,675 [>535-1,070] Mt of sediment from one submarine canyon, equivalent to 19–37 [>7–15] % of annual suspended sediment flux from present-day rivers. It was known earthquakes trigger canyon-flushing flows. We show river-floods also generate canyon-flushing flows, primed by rapid sediment-accumulation at the river-mouth, and sometimes triggered by spring tides weeks to months post-flood. It is demonstrated that strongly erosional turbidity currents self-accelerate, thereby travelling much further, validating a long-proposed theory. These observations explain highly-efficient organic carbon transfer, and have important implications for hazards to seabed cables, or deep-sea impacts of terrestrial climate change.

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Talling Peter J., Baker Megan L., Pope Ed L., Ruffell Sean C., Jacinto Ricardo Silva, Heijnen Maarten S., Hage Sophie, Simmons Stephen M., Hasenhündl Martin, Heerema Catharina J., McGhee Claire, Apprioual Ronan, Ferrant Anthony, Cartigny Matthieu J. B., Parsons Daniel R., Clare Michael A., Tshimanga Raphael M., Trigg Mark A., Cula Costa A., Faria Rui, Gaillot Arnaud, Bola Gode, Wallance Dec, Griffiths Allan, Nunny Robert, Urlaub Morelia, Peirce Christine, Burnett Richard, Neasham Jeffrey, Hilton Robert J. (2022). Longest sediment flows yet measured show how major rivers connect efficiently to deep sea. Nature Communications. 13 (1). 4193 (15p.). https://doi.org/10.1038/s41467-022-31689-3, https://archimer.ifremer.fr/doc/00786/89837/

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