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| Titel |
Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions |
| VerfasserIn |
M. Stabholz, X. Durrieu de Madron, M. Canals, A. Khripounoff, I. Taupier-Letage, P. Testor, S. Heussner, P. Kerhervé, N. Delsaut, L. Houpert, G. Lastras, B. Dennielou |
| 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. 2 ; Nr. 10, no. 2 (2013-02-19), S.1097-1116 |
| Datensatznummer |
250017521
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| Publikation (Nr.) |
 copernicus.org/bg-10-1097-2013.pdf |
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| Zusammenfassung |
| The deep outer margin of the Gulf of Lions and the adjacent basin, in the
western Mediterranean Sea, are regularly impacted by open-ocean convection,
a major hydrodynamic event responsible for the ventilation of the deep water
in the western Mediterranean Basin. However, the impact of open-ocean
convection on the flux and transport of particulate matter remains poorly
understood. The variability of water mass properties (i.e., temperature and
salinity), currents, and particle fluxes were monitored between September
2007 and April 2009 at five instrumented mooring lines deployed between 2050
and 2350-m depth in the deepest continental margin and adjacent basin. Four
of the lines followed a NW–SE transect, while the fifth one was located on a
sediment wave field to the west. The results of the main, central line
SC2350 ("LION") located at 42°02.5′ N, 4°41′ E, at
2350-m depth, show that open-ocean convection reached mid-water depth
(≈ 1000-m depth) during winter 2007–2008, and reached the seabed
(≈ 2350-m depth) during winter 2008–2009. Horizontal currents were
unusually strong with speeds up to 39 cm s−1 during winter 2008–2009. The
measurements at all 5 different locations indicate that mid-depth and
near-bottom currents and particle fluxes gave relatively consistent values
of similar magnitude across the study area except during winter 2008–2009,
when near-bottom fluxes abruptly increased by one to two orders of
magnitude. Particulate organic carbon contents, which generally vary between
3 and 5%, were abnormally low (≤ 1%) during winter 2008–2009 and
approached those observed in surface sediments (≈ 0.6%).
Turbidity profiles made in the region demonstrated the existence of a bottom
nepheloid layer, several hundred meters thick, and related to the
resuspension of bottom sediments. These observations support the view that
open-ocean deep convection events in the Gulf of Lions can cause significant
remobilization of sediments in the deep outer margin and the basin, with a
subsequent alteration of the seabed likely impacting the functioning of the
deep-sea ecosystem. |
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