Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions
|Author(s)||Stabholz M.1, 2, Durrieu De Madron X.1, Canals M.2, Khripounoff Alexis3, Taupier-Letage Isabelle4, Testor Pierre5, Heussner S.1, Kerherve P.1, Delsaut N.1, Houpert Loic1, Lastras G.2, Dennielou Bernard6|
|Affiliation(s)||1 : Univ Perpignan, CEFREM, CNRS, UMR 5110, F-66860 Perpignan, France.
2 : Univ Barcelona, Dept Estratig Paleontol & Geociencies Marines, GRC Geociencies Marines, E-08028 Barcelona, Spain.
3 : IFREMER, Dept EEP LEP, Ctr Bretagne, F-29280 Plouzane, France.
4 : Univ Sud Toulon Var, Aix Marseille Univ, CNRS, INSU,IRD,MIO,UMR 6117,UM 110, F-83507 La Seyne Sur Mer, France.
5 : Univ Paris 06, LOCEAN, CNRS, IRD,UMR 7159, F-75252 Paris, France.
6 : IFREMER, Unite Rech Geosci Marines, F-29280 Plouzane, France.
|Source||Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2013-02-19 , Vol. 10 , N. 2 , P. 1097-1116|
|WOS© Times Cited||49|
|Note||Special issue Deep-sea ecosystems in European seas|
|Abstract||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 degrees 02.5' N, 4 degrees 41' E, at 2350-m depth, show that open-ocean convection reached mid-water depth (approximate to 1000-m depth) during winter 2007-2008, and reached the seabed (approximate to 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 (approximate to 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.|