Flushing submarine canyons : Abstract : Nature

Nature 444, 354-357 (16 November 2006) | doi:10.1038/nature05271; Received 4 July 2006; Accepted 13 September 2006

Flushing submarine canyons

Miquel Canals¹, Pere Puig², Xavier Durrieu de Madron³, Serge Heussner³, Albert Palanques² & Joan Fabres^1,⁴

CRG Marine Geosciences, Department of Stratigraphy, Paleontology and Marine Geosciences, University of Barcelona, E-08028 Barcelona, Spain
Marine Sciences Institute, CSIC, E-08003 Barcelona, Spain
CEFREM, UMR 5110 CNRS-University of Perpignan, F-66860 Perpignan Cedex, France
Present address: Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794-5000, USA.

Correspondence to: Miquel Canals¹ Correspondence and requests for materials should be addressed to M.C. (Email: miquelcanals@ub.edu).

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 flows^2–5, 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 margins^6–8. 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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