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| Titel |
Sediment transport along the Cap de Creus Canyon flank during a mild, wet winter |
| VerfasserIn |
J. Martin, X. Durrieu de Madron, P. Puig, F. Bourrin, A. Palanques, L. Houpert, M. Higueras, A. Sanchez-Vidal, A. M. Calafat, M. Canals, S. Heussner, N. Delsaut, C. Sotin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 5 ; Nr. 10, no. 5 (2013-05-14), S.3221-3239 |
| Datensatznummer |
250018248
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| Publikation (Nr.) |
 copernicus.org/bg-10-3221-2013.pdf |
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| Zusammenfassung |
| Cap de Creus Canyon (CCC) is known as a preferential conduit for particulate
matter leaving the Gulf of Lion continental shelf towards the slope and the
basin, particularly in winter when storms and dense shelf water cascading
coalesce to enhance the seaward export of shelf waters. During the CASCADE
(CAscading, Storm, Convection, Advection and Downwelling Events) cruise in
March 2011, deployments of recording instruments within the canyon and
vertical profiling of the water column properties were conducted to study
with high spatial-temporal resolution the impact of such processes on
particulate matter fluxes. In the context of the mild and wet 2010–2011
winter, no remarkable dense shelf water formation was observed. On the other
hand, the experimental setup allowed for the study of the impact of E-SE
storms on the hydrographical structure and the particulate matter fluxes in
the CCC. The most remarkable feature in terms of sediment transport was a
period of dominant E-SE winds from 12 to 16 March, including two moderate
storms (maximum significant wave heights = 4.1–4.6 m). During this
period, a plume of freshened, relatively cold and turbid water flowed at high
speeds along the southern flank of the CCC in an approximate depth range of
150–350 m. The density of this water mass was lighter than the ambient
water in the canyon, indicating that it did not cascade off-shelf and that it
merely downwelled into the canyon forced by the strong cyclonic circulation
induced over the shelf during the storms and by the subsequent accumulation
of seawater along the coast. Suspended sediment load in this turbid intrusion
recorded along the southern canyon flank oscillated between 10 and
50 mg L−1, and maximum currents speeds reached values up to
90 cm s−1. A rough estimation of 105 tons of sediment was
transported through the canyon along its southern wall during a 3-day-long
period of storm-induced downwelling. Following the veering of the wind
direction (from SE to NW) on 16 March, downwelling ceased, currents inside
the canyon reversed from down- to up-canyon, and the turbid shelf plume was
evacuated from the canyon, most probably flowing along the southern canyon
flank and being entrained by the general SW circulation after leaving the
canyon confinement. This study highlights that remarkable sediment transport
occurs in the CCC, and particularly along its southern flank, even during
mild and wet winters, in absence of cascading and under limited external
forcing. The sediment transport associated with eastern storms like the ones
described in this paper tends to enter the canyon by its downstream flank,
partially affecting the canyon head region. Sediment transport during these
events is not constrained near the seafloor but distributed in a depth range
of 200–300 m above the bottom. Our paper broadens the understanding of the
complex set of atmosphere-driven sediment transport processes acting in this
highly dynamic area of the northwestern Mediterranean Sea. |
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