Letter | Published:

Flushing submarine canyons

Naturevolume 444pages354357 (2006) | Download Citation

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Abstract

The continental slope is a steep, narrow fringe separating the coastal zone from the deep ocean. During low sea-level stands, slides and dense, sediment-laden flows erode the outer continental shelf and the continental slope, leading to the formation of submarine canyons that funnel large volumes of sediment and organic matter from shallow regions to the deep ocean1. During high sea-level stands, such as at present, these canyons still experience occasional sediment gravity flows2–5, which are usually thought to be triggered by sediment failure or river flooding. Here we present observations from a submarine canyon on the Gulf of Lions margin, in the northwest Mediterranean Sea, that demonstrate that these flows can also be triggered by dense shelf water cascading (DSWC)—a type of current that is driven solely by seawater density contrast. Our results show that DSWC can transport large amounts of water and sediment, reshape submarine canyon floors and rapidly affect the deep-sea environment. This cascading is seasonal, resulting from the formation of dense water by cooling and/or evaporation, and occurs on both high- and low-latitude continental margins6–8. DSWC may therefore transport large amounts of sediment and organic matter to the deep ocean. Furthermore, changes in the frequency and intensity of DSWC driven by future climate change may have a significant impact on the supply of organic matter to deep-sea ecosystems and on the amount of carbon stored on continental margins and in ocean basins.

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Acknowledgements

This work was supported by the European Commission (EUROSTRATAFORM, EURODOM and HERMES projects), the Office of Naval Research, CNRS-INSU and the Catalan Government. Sediment cohesion data were provided by N. Sultan, N data by T. Tesi, and DOC data by M. Pujo-Pay. Multibeam bathymetry was collected in cooperation with Fugro Survey Ltd and AOA Geophysics. Contributions of the scientific and technical staff at the authors’ home institutions are warmly acknowledged. Author Contributions All authors contributed to the design and implementation of the experimental strategy. M.C. steered the integration and joint analysis of the data, interpreted side scan sonar data and wrote the final version of the paper in cooperation with S.H. P.P., X.D.d.M. and A.P. took the responsibility for time series, X.D.d.M. for hydrology data, and S.H. and J.F. for sediment trap data. All authors discussed the results and commented on the manuscript.

Author information

Author notes

    • Joan Fabres

    Present address: Marine Sciences Research Center, Stony Brook University, Stony Brook, New York, 11794-5000, USA

Affiliations

  1. CRG Marine Geosciences, Department of Stratigraphy, Paleontology and Marine Geosciences, University of Barcelona, E-08028, Barcelona, Spain

    • Miquel Canals
    •  & Joan Fabres
  2. Marine Sciences Institute, CSIC, E-08003, Barcelona, Spain

    • Pere Puig
    •  & Albert Palanques
  3. CEFREM, UMR 5110 CNRS-University of Perpignan, F-66860, Perpignan Cedex, France

    • Xavier Durrieu de Madron
    •  & Serge Heussner

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Competing interests

Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests.

Corresponding author

Correspondence to Miquel Canals.

Supplementary information

  1. Supplementary Notes

    This file contains Supplementary Methods and Supplementary Figure Legends. (DOC 30 kb)

  2. Supplementary Figure 1

    Long term records from the Lacaze-Duthiers Canyon since October 1993. (PDF 21902 kb)

  3. Supplementary Figure 2

    Time integrated along-canyon cumulative suspended sediment transport for seven submarine canyons in the Gulf of Lion. (PDF 80 kb)

  4. Supplementary Figure 3

    Near-bottom time series of potential temperature, potential density anomaly, current speed and suspended sediment concentration. (PDF 219 kb)

  5. Supplementary Figure 4

    Time series before cascading (a) and during cascading (b) in winter 2004-05. (PDF 105 kb)

  6. Supplementary Figure 5

    C/N regression fit for trap particles collected in the Cap de Creus and Lacaze-Duthiers canyons during autumn stratified conditions and DSWC events. (PDF 126 kb)

  7. Supplementary Figure 6

    Coastal regions in the world where DSWC has been observed. (PDF 1110 kb)

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https://doi.org/10.1038/nature05271

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