Hydrological changes in the Ligurian Sea (NW Mediterranean, DYFAMED site) during 1995–2007 and biogeochemical consequences

Marty, Jean-Claude; Chiavérini, Jacques

doi:10.5194/bg-7-2117-2010

Cited by 121 publications

(165 citation statements)

References 46 publications

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“…The eastern part of the basin (i.e., the Ligurian Sea) is generally an area of intermediate to deep mixing (200-1000 m) subjected to an important year-to-year variability [Marty and Chiaverini, 2010]. In the absence of a highly instrumented mooring line like in the Gulf of Lions, the sampling of the Ligurian Sea is sparser.…”

Section: 1002/2016jc012144mentioning

confidence: 99%

Scales and dynamics of Submesoscale Coherent Vortices formed by deep convection in the northwestern Mediterranean Sea

et al. 2016

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Since 2010, an intense effort in the collection of in situ observations has been carried out in the northwestern Mediterranean Sea thanks to gliders, profiling floats, regular cruises, and mooring lines. This integrated observing system enabled a year‐to‐year monitoring of the deep waters formation that occurred in the Gulf of Lions area during four consecutive winters (2010–2013). Vortical structures remnant of wintertime deep vertical mixing events were regularly sampled by the different observing platforms. These are Submesoscale Coherent Vortices (SCVs) characterized by a small radius (∼5–8 km), strong depth‐intensified orbital velocities (∼10–20 cm s−1) with often a weak surface signature, high Rossby (∼0.5) and Burger numbers O(0.5–1). Anticyclones transport convected waters resulting from intermediate (∼300 m) to deep (∼2000 m) vertical mixing. Cyclones are characterized by a 500–1000 m thick layer of weakly stratified deep waters (or bottom waters that cascaded from the shelf of the Gulf of Lions in 2012) extending down to the bottom of the ocean at ∼2500 m. The formation of cyclonic eddies seems to be favored by bottom‐reaching convection occurring during the study period or cascading events reaching the abyssal plain. We confirm the prominent role of anticyclonic SCVs and shed light on the important role of cyclonic SCVs in the spreading of a significant amount (∼30%) of the newly formed deep waters away from the winter mixing areas. Since they can survive until the following winter, they can potentially have a great impact on the mixed layer deepening through a local preconditioning effect.

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Section: 1002/2016jc012144mentioning

confidence: 99%

Scales and dynamics of Submesoscale Coherent Vortices formed by deep convection in the northwestern Mediterranean Sea

et al. 2016

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“…While deep OOC is very infrequent in the Ligurian Sea (one single event for the 1995-2007 period as observed by Marty and Chiavérini, 2010) and thus rarely affects the deep sediment (Martin et al, 2010). On the contrary, the recurrent deep OOC events in the Gulf of Lions continuously rework bottom sediments and a long-term alteration of the sediment might be expected.…”

Section: Impacts Of Open-ocean Deep Convection Events On Seabed and Bmentioning

confidence: 99%

Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions

et al. 2013

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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<sup>−1</sup> 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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“…Three compartments of autotrophs from the smallest to the largest are accounted for: (1) pico-autotrophs, mainly Synechococcus (0.7-2 µm, Phy 1 in the model); (2) nanophytoplankton (2-20 µm, Phy 2 in the model) that dominate the biomass of phytoplankton assemblages for most of the year (Marty et al, 2002;Marty and Chiavérini, 2010) -this compartment is an assemblage of heterogeneous taxonomic composition (for example autotrophic dinoflagellates); and (3) microphytoplankton community (20-200 µm, Phy 3 in the model) largely dominated by phytoplankton silicifiers (mainly diatoms) that can punctually contribute to a significant part of primary production and biomass during spring bloom in the NW Mediterranean Sea (Marty et al, 2002;Marty and Chiavérini, 2010). The main functional role of the latter group lies in their ability to contribute to matter export directly through direct shell and indirectly through fecal pellets sedimentation (via copepods grazing).…”

Section: Ecosystem Modelmentioning

confidence: 99%

Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

et al. 2011

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Abstract.A coupled hydrodynamic-biogeochemical modelling is developed to address main mechanisms that drive the particulate organic carbon (POC) deposition in the Gulf of Lions (NW-Mediterranean). Low-salinity water (LSW, salinity <37.5) lenses detached from the Rhone River plume under specific wind conditions tend to favour the biological productivity and provide a good opportunity for validating a planktonic ecosystem modelling. A specific calibration dedicated to river plume ecosystems is then proposed and validated using in situ measurements within such LSW lens (BIOPRHOFI cruise -May 2006) and on the Gulf of Lions. During spring 2006, the POC deposition is maximal on the prodelta area and within the coastal area in the Gulf of Lions. Organic detritus mostly contribute to the total POC deposition (82-92 %) whereas the contribution of living organisms (microphytoplankton) appears lower than 17 %. Exploring both influences of terrestrial inputs from the Rhone River and planktonic ecosystems on the POC deposition on the shelf, we estimated that the contribution of terrestrial POM inputs to the total POC deposition is lower than 17 % at the shelf scale during the study period, with maxima during peak discharges of the Rhone River. The main deposition area of terrestrial POC is found in the vicinity of the river mouth in agreement with sediment data. On the other hand, a remarkable influence of marine biological processes on the POC deposition is highlighted further on the shelf (from 60 to 80 m depth). A tight feedback between zooplankton and POM contents in the water column is proposed to explain Correspondence to: P. A. Auger (pierre-amael.auger@aero.obs-mip.fr) the control of POC deposition by zooplankton: terrestrial POM inputs would favour the development of living organisms through photosynthesis and grazing processes increasing the retention of organic matter within the food web. By favouring the development of large-sized zooplankton, LSW lenses may have paradoxically a negative impact on the carbon deposition on the shelf. In the same way, peak discharges of the Rhone River finally increase the gradient of POC deposition between the prodelta and the offshore area in the Gulf of Lions. The biogenic elements from the Rhone River are then exported further offshore through advection of zooplankton communities on the Gulf of Lions shelf.

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Hydrological changes in the Ligurian Sea (NW Mediterranean, DYFAMED site) during 1995–2007 and biogeochemical consequences

Abstract: Abstract. Data obtained during the monthly cruises of the DYFAMED time-series study (northwestern MediterraneanSea

Cited by 121 publications

References 46 publications

Scales and dynamics of Submesoscale Coherent Vortices formed by deep convection in the northwestern Mediterranean Sea

Scales and dynamics of Submesoscale Coherent Vortices formed by deep convection in the northwestern Mediterranean Sea

Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions

Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

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