On the dynamics of surface cold filaments in the Mediterranean Sea

Bignami, Fabio; Böhm, E.; D'Acunzo, Emma; D’Archino, Roberta; Salusti, E.

doi:10.1016/j.jmarsys.2008.03.002

Cited by 24 publications

(27 citation statements)

References 34 publications

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“…By choosing sediment concentration as a nonconserved scalar property of the flow, we derived a new potential vorticity using the Ertel [1942] theorem that predicts sedimentation downstream of a river mouth as a result of initial conditions at the mouth. As known from physical oceanography, high-PV jets preserve their filament shape because of minimal mixing with ambient water at jet margins [Holland, 1967;Haynes and McIntyre, 1990;Bignami et al, 2008]. For high-PV sediment-laden riverine jets this feature can be seen as the ability of the system to maintain a well pronounced Gaussian horizontal velocity profile (and the related horizontal shear stress), which limits sediment deposition along the jet centerline as confirmed in recent experimental works.…”

Section: Discussionmentioning

confidence: 99%

“…Since detailed measurements of flow and sediment transport at river mouths are limited, in this paper we will employ satellite observations of sea surface temperature and ocean color to examine the hydrodynamics and sediment concentration of river outflows. We observe a qualitative similarity between elongate channel jets and cold oceanic filaments [Bignami et al, 2008], which are shallow veins of wind-sheared water having high potential vorticity and low lateral spreading (Figure 4). This similarity provides the basis for a new modeling approach, in which we adapt geophysical fluid dynamics theory from oceanography to describe river mouth jets.…”

Section: Introductionmentioning

confidence: 99%

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A potential vorticity theory for the formation of elongate channels in river deltas and lakes

Falcini

Jerolmack

2010

J. Geophys. Res.

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[1] Rivers empty into oceans and lakes as turbulent sediment-laden jets, which can be characterized by a Gaussian horizontal velocity profile that spreads and decays downstream because of shearing and lateral mixing at the jet margins. Recent experiments demonstrate that this velocity field controls river-mouth sedimentation patterns. In nature, diffuse jets are associated with mouth bar deposition forming bifurcating distributary networks, while focused jets are associated with levee deposition and the growth of elongate channels that do not bifurcate. River outflows from elongate channels are similar in structure to cold filaments observed in ocean currents, where high potential vorticity helps to preserve coherent structure over large distances. Motivated by these observations, we propose a hydrodynamic theory that seeks to predict the conditions under which elongate channels form. Our approach models jet velocity patterns using the flow vorticity. Both shearing and lateral spreading are directly related to the vertical component of vorticity. We introduce a new kind of potential vorticity that incorporates sediment concentration and thus allows study of jet sedimentation patterns. The potential vorticity equation reduces the number of fluid momentum equations to one without losing generality. This results in a compact analytical solution capable of describing the streamwise evolution of the potential vorticity of a sediment-laden jet from initial conditions at the river mouth. Our theory predicts that high potential vorticity is a necessary condition for focused levee deposition and the creation of elongate channels. Comparison to numerical, laboratory, and field studies indicates that potential vorticity is a primary control on channel morphology. Our results may be useful for designing river delta restoration schemes such as the proposed Mississippi Delta diversion.Citation: Falcini, F., and D. J. Jerolmack (2010), A potential vorticity theory for the formation of elongate channels in river deltas and lakes,

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A potential vorticity theory for the formation of elongate channels in river deltas and lakes

Falcini

Jerolmack

2010

J. Geophys. Res.

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“…Therefore, upwelling areas do not display a striking difference in biological production as compared to other active areas of the basin. By contrast, in situ observations and modeling studies suggest that mesoscale and submesoscale processes may affect biological activity in the MS, namely in: i) active frontal regions (North BalearicCatalan, Almeria-Oran, North-East Aegean Sea Fronts) (e.g., Estrada and Salat, 1989;Estrada, 1991;Zervoudaki et al, 2007), ii) deep convection areas (Gulf of Lion, South Adriatic Gyre, Rhodos Gyre) (e.g., Lévy et al, 1998a,b;SiokouFrangou et al, 1999;Gacic et al, 2002), and iii) sites where coastal morphology and intense wind stress generate a strong input of potential vorticity that leads to the formation of energetic filaments (Wang et al, 1988;Bignami et al, 2008). The latter process may significantly contribute to the dispersal of coastal inputs toward the open sea, along with plankton.…”

Section: Physical and Chemical Frameworkmentioning

confidence: 99%

Plankton in the open Mediterranean Sea: a review

et al. 2010

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Abstract. We present an overview of the plankton studies conducted during the last 25 years in the epipelagic offshore waters of the Mediterranean Sea. This quasi-enclosed sea is characterized by a rich and complex physical dynamics with distinctive traits, especially in regard to the thermohaline circulation. Recent investigations have basically confirmed the long-recognised oligotrophic nature of this sea, which increases along both the west-east and the north-south directions. Nutrient availability is low, especially for phosphorous (N:P up to 60), though this limitation may be buffered by inputs from highly populated coasts and from the atmosphere. Phytoplankton biomass, as chl a, generally displays low values (less than 0.2 µg chl a l −1 ) over large areas, with a modest late winter increase. A large bloom (up to 3 µg l −1 ) is observed throughout the late winter and spring exclusively in the NW area. Relatively high biomass values are recorded in fronts and cyclonic gyres. A deep chlorophyll maximum is a permanent feature for the whole basin, except during the late winter mixing. It is found at increasingly greater depths ranging from 30 m in the Alboran Sea to 120 m in the easternmost Levantine basin. Primary production reveals a west-east decreasing trend and ranges between 59 and 150 g C m −2 y −1 (in situ measurements). Overall, the basin is largely dominated by small autotrophs, microheterotrophs and egg-carrying copepod species. The microorganisms (phytoplankton, viruses, bacteria, flagellates and ciliates) and zooplankton components reveal a considerable diversity and

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“…The challenges of characterizing the FZFE processes imply precise and high-resolution observations in addition to a multi-sensor approach on several spatial/temporal scales. Thermal NOAA/AVHRR satellite images were used to identify sites of highest frequency in cold filaments in the Mediterranean Sea (Bignami et al, 2008) and transport patterns were studied using satelite altimetry and Lagrangian numerical analysis in the open sea (d'Ovidio et al, 2004). This methodology was adapted to the coastal area using in situ observations to correct for the uncertainties connected to satelite altimetry data close to shore (Nencioli et al, 2011).…”

Section: Present Knowledgementioning

confidence: 99%

Physical forcing and physical/biochemical variability of the Mediterranean Sea: a review of unresolved issues and directions for future research

Artale²,

et al. 2014

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Abstract. This paper is the outcome of a workshop held in Rome in November 2011 on the occasion of the 25th anniversary of the POEM (Physical Oceanography of the Eastern Mediterranean) program. In the workshop discussions, a number of unresolved issues were identified for the physical and biogeochemical properties of the Mediterranean Sea as a whole, i.e., comprising the Western and Eastern sub-basins. Over the successive two years, the related ideas were discussed among the group of scientists who participated in the workshop and who have contributed to the writing of this paper.Three major topics were identified, each of them being the object of a section divided into a number of different subsections, each addressing a specific physical, chemical or biological issue:1. Assessment of basin-wide physical/biochemical properties, of their variability and interactions.2. Relative importance of external forcing functions (wind stress, heat/moisture fluxes, forcing through straits) vs. internal variability.3. Shelf/deep sea interactions and exchanges of physical/biogeochemical properties and how they affect the sub-basin circulation and property distribution.Furthermore, a number of unresolved scientific/methodological issues were also identified and are reported in each sub-section after a short discussion of the present knowledge. They represent the collegial consensus of the scientists contributing to the paper. Naturally, the unresolved issues presented here constitute the choice of the authors and therefore they may not be exhaustive and/or complete. The overall goal is to stimulate a broader interdisciplinary discussion among the scientists of the Mediterranean oceanographic community, leading to enhanced collaborative efforts and exciting future discoveries.

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On the dynamics of surface cold filaments in the Mediterranean Sea

Cited by 24 publications

References 34 publications

A potential vorticity theory for the formation of elongate channels in river deltas and lakes

A potential vorticity theory for the formation of elongate channels in river deltas and lakes

Plankton in the open Mediterranean Sea: a review

Physical forcing and physical/biochemical variability of the Mediterranean Sea: a review of unresolved issues and directions for future research

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