What don’t we know about dying and dead seas ?

Conference (2003, May)

As conclusions of this NATO Advanced Research Workshop on Dying and Dead Seas, numerous questions remains concerning the various studied water bodies, all along their hydrological cycle and along their ... [more ▼]

As conclusions of this NATO Advanced Research Workshop on Dying and Dead Seas, numerous questions remains concerning the various studied water bodies, all along their hydrological cycle and along their anthropic perturbations. A synthesis of most important open questions is presented. [less ▲]

Influence of the Aral Sea negative water balance on its seasonal circulation : use of a 3D hydrodynamic model

Conference (2003, May)

Modelling the Danube-influenced North-western continental shelf of the Black Sea. I: Hydrodynamical processes simulated by 3-D and box models

in Estuarine Coastal & Shelf Science (2002), 54(3), 453-472

A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of ... [more ▼]

A hydrodynamical modelling of the Black Sea is presented using the GHER 3-D primitive equation model. Results of a very high resolution model with 5 km grid size are analysed and the dominant features of general circulation in the Black Sea are highlighted. Compared with a coarse resolution model, forced with the same climatic monthly averaged atmospheric data, the high resolution model exhibits stronger variability, including frontal structures and coastal upwellings induced by baroclinic instabilities, in particular along the Turkish coast. A comparison of the shelf-open sea exchanges, with particular focus on the cold intermediate waters, shows that both models lead to a replenishment of the CIL in the basin interior by cold waters formed on the shelf. Due to the better representation of frontal structures, the high resolution model is an appropriate candidate for coupling with a biological model. Problems of calibration, interpretation and data availability typically arise from this kind of coupled 3-D model. In order to overcome such difficulties, the results of the 3-D hydrodynamical model are used to guide the development of an integrated 0-D box model capable of achieving the objectives of projects like EROS21, where the effect of changes in the Danube inflows on the shelf ecosystem is investigated. The 0-D model is thus designed to cover this region and is obtained through integration over an appropriate variable volume. The integration procedure shows where the weaknesses of an 0-D approach might lie. Diagnoses in the 3-D model of the integral quantities show the range of uncertainty one can expect in the exchange laws of the 0-D model. (C) 2002 Elsevier Science Ltd. All rights reserved. [less ▲]

Modelling nitrogen fluxes in a semi-enclosed environment (the Black Sea): transport versus biogeochemical processes and quantification of the exchanges at the shelf break

in Commission internationale pour l'exportation Scientifique de la Mer Méditerranée Vol. 36 (2001)

A three-dimensional coupled biogeochemical-hydrodynamical model has been developed to get a better understanding of the biogeochemical functioning of the Black Sea. The in?uence on the ecodynamics of ... [more ▼]

A three-dimensional coupled biogeochemical-hydrodynamical model has been developed to get a better understanding of the biogeochemical functioning of the Black Sea. The in?uence on the ecodynamics of hydrodynamical and biogeochemical processes is quantified. Nitrogen inputs from the rivers, from the sediments and from the deep sea are estimated and compared in terms of potential fertilization. The exchanges between the north-western shelf and the deep sea are quantified. The results illustrate a highly complex spatial variability of the phytoplankton annual cycle and thus, stress the importance of using a 3D model to capture the essential physical-biological interactions that explain the data. [less ▲]

Sensitivity of the black sea's ecosystem to physical processes: first results of a high resolution 3D interdisciplinary model

in Balopoulos, E.; Chronis, G.; Lipiatou, E. (Eds.) et al International conference. Oceanography of the eastern Mediterranean and Black Sea. Similarities and differences of two interconnected basins (2000)

A hydrodynamical model of the general circulation in the Black Sea has been build up, using the GHER (GeoHydrodynamics and Environment Research) three-dimensional, non-linear, baroclinic, turbulent ... [more ▼]

A hydrodynamical model of the general circulation in the Black Sea has been build up, using the GHER (GeoHydrodynamics and Environment Research) three-dimensional, non-linear, baroclinic, turbulent closure model. A model with 5 km horizontal resolution and 25 vertical levels is used to compute the typical seasonal cycle by forcing the model with climatological monthly mean fields of temperature, salinity and wind stress at the air-sea interface. Furthermore, the river discharges of the Danube, the Dnestr and the Dnepr are taken into account. This high resolulion model resolves the baroclinic instabilities generated by the interactions of the boundary current with the coastline geometry or with the continental shelf/slope topography. A simple ecosystem model defined by a nitrogen cycle is coupled with Ihe hydrodynamical model. The state variables of this model are defined as those which are necessary and sufficient to assess the effects of the physical processes, and in particular of the boundary current instability , on the space time distribution of the primary and secondary productions. The results of the 3D ecohydrodynamic model are compared with CZCS data of surface chlorophyll fields collected during the period from 1978 to 1986. [less ▲]

Dissection of the GHER turbulence closure scheme

in Journal of Marine Systems (1999), 21(1-4), 379-397

In this paper, the turbulence closure scheme implemented in the GHER hydrodynamic model is described in detail. Two case studies carried out in two contrasting conditions-one in the shallow, tide ... [more ▼]

In this paper, the turbulence closure scheme implemented in the GHER hydrodynamic model is described in detail. Two case studies carried out in two contrasting conditions-one in the shallow, tide dominated, north-western European continental shelf, and the other in the deep Mediterranean Sea-are used to identify the dominant terms of the equation for the turbulent kinetic energy, first theoretically, secondly from the results of the simulations. In both domains, the dominant terms are the local destruction and production terms, the vertical diffusion term and to a smaller degree, the time derivative. Advection and horizontal diffusion turn out to be negligible in most of the relevant cases for such large scale studies. This opens the way to simplifications and optimisations of the numerical models. (C) 1999 Elsevier Science B.V. All rights reserved. [less ▲]

Coupled 3D eddy-resolving general circulation model and ecosystem model applied to the Black sea.

in Ostrovskii, S.; Zatsepin, A. (Eds.) Oceanic Fronts and Related Phenomena (Konstantin Federov International Memorial Symposium) (1999)

Simulation of the annual plankton productivity cycle in the Black Sea with a 3D high resolution interdisciplinary model

in Papailiou, K.D.; Tsahalis, D.; Periaux, J. (Eds.) et al Proceedings of the 4th European Computational Fluid Dynamics Conference (ECCOMAS) (1998)

Interdisciplinary approach and data assimilation in a Mediterranean ecosystem model

in EOS Transactions (1998), 79

Reconnaissance of the main Black Sea's ecohydrodynamics by means of a 3D interdisciplinary model

in Journal of Marine Systems (1998), 16(1-2), 85-105

A 3D interdisciplinary model has been used to test the sensitivity of the Black Sea’s ecosystem to physical processes. The hydrodynamical model of the general circulation has been built up, using the GHER ... [more ▼]

A 3D interdisciplinary model has been used to test the sensitivity of the Black Sea’s ecosystem to physical processes. The hydrodynamical model of the general circulation has been built up, using the GHER primitive equation model. A model with 15 km horizontal resolution and 25 vertical levels is used to compute the typical seasonal cycle. The model is forced by climatological monthly mean fields of temperature, salinity and wind stress at the air–sea interface; the river discharges of the Danube, Dnestr and Dnepr are taken into account. An ecosystem model at basin scale is then defined by a nitrogen cycle considering several phytoplankton and zooplankton sizes and including the microbial loop. The ecosystem model is embedded on-line into the 3D hydrodynamical model with a superimposed cycle for the light intensity. This model must be regarded rather as a first tool for testing the coupling of hydrodynamic and ecosystem submodels, while acquiring some preparatory assessment of the effect of physical processes on the ecodynamics. The results display a highly three-dimensional aspect with important horizontal and vertical variations, obviously imparted to the system by the physical processes horizontal and vertical advection, vertical mixing and diffusion, upwelling associated with light limitation at depth and sinking of dead organisms. In this paper, the results are described emphasizing the effects of the hydrodynamic constraints on the space–time distribution of the primary and secondary production. [less ▲]