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Contenu archivé le 2022-12-23

Physical parameterizations and climate response

Objectif



Parameterizations of vertical mixing in existing Black Sea models are based on the use of a vertical eddy viscosity coefficient, an approach not efficient enough to describe mixing processes in strongly stratified seas. Data obtained in the Black Sea during the past decade shows that better parameterizations of convection and upper layer mixing are needed to model realistically the large-scale circulation, the interaction between the surface layer and deep layers, and the dispersion of tracers in the open sea. A characteristic feature of the Black Sea stratification is the sharp halocline separating a low salinity upper layer from higher salinity below 150 m, with a temperature minimum, refered to as the Cold Intermediate Layer (CIL) between the halocline & the seasonal thermocline The relevant physical mechanisms are described as follows. The CIL is generated bY convection occurring during winter in regions where relatively warm saline waters are upwelled to the surfaces, in the centres of large-scale cyclonic circulations in the open sea and over continental shele slopes. As the upwelling waters mix with the fresh and cold surface waters, density increases and triggers convective mixing. In addition, cold dense waters from the surface mixed layer creep down along isopycnal surfaces, forming the CIL above the halocline. Deepening of these waters result in a strengthening of eddy currents.
Research work will be focused on studying and parameterizing the following processes :
- Mixing of two water masses with different temperature and salinity ; - Isopycnic creeping.
A linear model will be used, of the type described in Frankignoul and Muller (1979). The depth and rate of isopycnal creeping will be defined as functions of temperature, salinity and large-scale velocity. This research work will usefullv interact with the research work by Participant 8 (P. HAUGAN)

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Régime de financement

CSC - Cost-sharing contracts

Coordinateur

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
Contribution de l’UE
Aucune donnée
Adresse
Ecole Polytechnique
91128 PALAISEAU
France

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Participants (1)