The Gulf of Lions' hydrodynamics

Millot, Claude

doi:10.1016/0278-4343(90)90065-t

Cited by 350 publications

(296 citation statements)

References 4 publications

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“…The present sediment trap data indicate that the water column biogenic silica as well as the Si production rates measured in situ are likely to be underestimated for the SOFi site (Leblanc et al, 2003) and that the downward material flux occurs with a high temporal variability, which can be seen as short pulses of sedimentation and drastic flux increases over only a few days. This short-term variability has been described in previous studies as the result of several forcing events such as the Rhône River inputs, the strong wind regimes in the Gulf of Lions, internal waves, resuspension events, variations of the path of the NMC (Millot, 1990) and rapid changes in the light and nutrient regimes, which allows phytoplankton to bloom outside of the productive period . Thus a rotation period of the sediment trap cups of 3 to 4 days seems to be close to the minimum interval required to accurately accurately monitor the pulse-like biological events taking place in the Gulf of Lions.…”

Section: Temporal Variability and Seasonalitysupporting

confidence: 55%

Efficiency of the silicate pump at a coastal oligotrophic site in the Mediterranean Sea

et al. 2005

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Abstract.A one-year survey of the sedimenting particulate material was conducted at the SOFi site located on the edge of the continental slope in the Gulf of Lions (Northwestern Mediterranean) between September 1999 and December 2000. The main focus of this paper was to establish an annual budget of biogenic silica export, to describe the seasonnal pattern of Si fluxes in relation to the organic and mineral C fluxes and to quantify the Si/C decoupling processes during sedimentation. The pattern of the downward flux of BSi was partly typical with increased daily sedimentation rates during spring followed by smaller peaks during summer. However, an unusual sedimentation event was recorded in the bottom trap in February before the spring thermal stratification occurred, and represented 37% of the annual BSi mass flux. The total annual BSi flux at the SOFi site was estimated from the bottom trap and amounted to 86.8 mmol Si m −2 y −1 , while the organic carbon flux amounted to 154.9 mmol C m −2 y −1 . The overall efficiency of C export to depth compared to surface primary production budgets was low (3%) and similar to values found for oligotrophic regions of the Eastern Mediterranean. On the other hand, we documented a very high efficiency of the Si export at the SOFi site, with 62% of the Si produced in the surface layer exported to the bottom trap. The excellent correlation between BSi and particulate organic C (POC) in the bottom trap further indicates that the bulk of the organic matter is transferred to depth in association with diatoms. However, the main fraction of the C produced by phytoplankton is lost in the water column through oxidation or metabolisation, while biogenic silica is more efficiently transferred to depth. This strong Si/C decoupling with depth is likely to be the cause of the spring Correspondence to: K. Leblanc (leblanc@com.univ-mrs.fr) depletion of silicic acid over the entire water column which was observed by mid-April in a companion study (Leblanc et al., 2003) and may cause a severe Si limitation of the diatom spring bloom in this oligotrophic region of the Gulf of Lions.

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Section: Temporal Variability and Seasonalitysupporting

confidence: 55%

Efficiency of the silicate pump at a coastal oligotrophic site in the Mediterranean Sea

et al. 2005

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“…Northern (Mistral) and northwestern (Tramontane) winds are known to generate classical oceanographic features such as up and downwelling currents (Millot, 1990) or inertial oscillations (Petrenko, 2003). Recent studies demonstrate the impact of exceptional events such as storms or intense period of cold and dry winds on the Gulf of Lions local hydrodynamic.…”

Section: Meteorological Forcingmentioning

confidence: 99%

Massive sand beds attributed to deposition by dense water cascades in the Bourcart canyon head, Gulf of Lions (northwestern Mediterranean Sea)

et al. 2006

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International audienceNowadays, the Gulf of Lions continental shelf and slope are under the influence of dense water cascading, wind-induced bottom currents and the geostrophic Northern Current. In order to characterize sedimentary activity at the shelf break, several interface and piston cores were taken in the Bourcart canyon head and a current meter equipped with temperature, conductivity, pressure and turbidity sensors was moored during the 2003–2004 winter season. Even if the canyon is not connected directly to continental sources since Last Glacial Maximum, detailed grain size, X-ray and sediment facies analysis of interface cores show that down to 350 m water depth, the canyon head is blanketed by up to 1.5 m of structureless muddy medium-grained sand. 210Pbexc activity measurements demonstrate present day sedimentary activity of the canyon head. Time series of currents with peak velocity reaching 0.37 m/s, suspended sediment concentration and temperature indicate that dense water cascading is the main process allowing the reworking, transport and accumulation of sand within the canyon head, even though winter 2003–2004 was characterized by low cascading events compared to other years. These sand beds, called “cascadite” constitute a new type of deposit that differs from other typical slope deposits (turbidites, hyperpycnites, contourites) in terms of flow duration and sedimentological characteristics. They are similar to shallow water contourites. They might be time-equivalent to the recent turbidites described throughout the deep western Gulf of Lions basin

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“…Input of continental water plays an important role in the region, especially from the outflow of the Rhône River, the largest river in the Western Mediterranean basin, which empties into the Gulf of Lions. In particular, the broad continental shelf off the Gulf of Lions (between 50 and 100 km) acts as a holding area for waters with salinity levels normally between 1 and 2 psu lower than those in the open sea (Millot, 1990;Salat et al, 1990). Furthermore, by decreasing the salinity of inshore waters in the region, the influxes of continental run-off help strengthen the structure of the shelf-slope density front associated with the Liguro-Provençal and Catalan Current (Font et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

Advection of continental water as an export mechanism for anchovy, Engraulis encrasicolus, larvae

Sabatés¹,

Salat²,

Olivar³

2001

Sci. Mar.

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SUMMARY: The presence of a surface layer of a less saline water of continental influence (CIW) along the continental slope off the Catalan coast (NW Mediterranean) was observed in June 1995. This CIW was formed in the Gulf of Lions from Rhône runoff and carried by the current associated with the shelf-slope front. This study analyses the spatio-temporal behaviour of that water of continental influence in relation to the shelf-slope front, and its effect on the distribution of fish larvae, in particular the larvae of the anchovy, Engraulis encrasicolus. Displacements of the front are observed to follow an oscillation with a period of eight days and an amplitude of 10 km. Anchovy larvae were associated with the presence of CIW, whereas the oceanic species Hygophum benoiti appeared in the region of the slope when the front, and the associated CIW layer, moved close inshore during its oscillation. The size frequency distribution for the anchovy larvae trapped within the CIW suggests that the larvae had been spawned further north, near the Gulf of Lions. It is concluded not only that larvae were transported by the current but also that their development had taken place entirely inside the CIW. The possible benefit to the survival of anchovy larvae of being kept inside that water, though they have been carried far from their spawning areas, is discussed in the basis of fluorescence and microzooplankton data.

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The Gulf of Lions' hydrodynamics

Cited by 350 publications

References 4 publications

Efficiency of the silicate pump at a coastal oligotrophic site in the Mediterranean Sea

Efficiency of the silicate pump at a coastal oligotrophic site in the Mediterranean Sea

Massive sand beds attributed to deposition by dense water cascades in the Bourcart canyon head, Gulf of Lions (northwestern Mediterranean Sea)

Advection of continental water as an export mechanism for anchovy, Engraulis encrasicolus, larvae

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