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Please use this identifier to cite or link to this item: http://hdl.handle.net/1834/3877

Title: Modelado numérico del ecosistema de los golfos norpatagónicos
Other Titles: Numerical modeling of the ecosystem of North-Patagonian gulfs
Authors: Tonini, M.H.
Theses advisor: Palma, E.D.
Cortinez, V.H.
ASFA Terms: Water masses
Oceanography
Currents (water)
Fronts
Ocean circulation
Mathematical models
Tides
Winds
Physical oceanography
Issue Date: 2010
Abstract: This dissertation analyses the oceanic circulation of the Norpatagonian Gulfs, a region of the Argentinean Sea that has long been recognized for the high productivity and biodiversity of the ecosystem. The study aims towards a systematic exploration of the physical processes that control the circulation using a high resolution three dimensional numerical model. To facilitate the dynamical understanding of the results our experimental strategy was to start with a constant density (barotropic) model forced by tides and winds, and to progress to a more complex case including density stratification generated by surface fluxes of heat and humidity. The main result that stems from the numerical experiments is that tidal forcing significantly contributes to the overall subtidal residual circulation both in the homogenous and stratified models. The barotropic model shows that the nonlinear interaction between the oscilating tide and bottom topography leads to the formation of several robust residual circulation patterns: basin gyres, bathymetric vortices and coastline cuadrupoles, whichs are formed by recirculating eddies at mouths of SJG and GN. With the exception of the winter months, when the winds are stronger, the barotropic ocean response is completely dominated by the cyclonic tidal residual. It is necessary to have a strong wind in the northerly or westerly direction to break that pattern. The results of the stratified model also shows the profound influence of the tides in shaping the annual cycle of the circulation inside San Matias Gulf. The overall circulation pattern is dominated by a strong cyclonic gyre (composed by two recirculating sub-gyres) during summer with smaller anticyclonic gyres on the southwest coast and north of Valdes Peninsula. The spinup of the cyclonic circulation between October and February is caused by the interaction of the tides and stratification (generated by surface heat fluxes) in the presence of variable topography. As a result of this closed circulation the Gulf is almost isolated from the shelf during summer. From March to September the stratification is eroded and the northern subgyre spins down and gradually shrinks in size being absorbed by the southern subgyre. Simultaneously, the western sector of the Gulf is occupied by an anticyclonic gyre. The inclusion of wind forcing does not substantially modified the structure and intensity of the summer gyres but strengthens both the cyclonic and anticyclonic circulation during fall-winter. There is a similar oceanic response in Nuevo Gulf, but in this case there is only one year-round cyclonic gyre that intensifies in summer and is reduced in spatial extension in winter with the appearence of a weak anticyclonic gyre in the western coast. The residual currents are dominated by a strong year-round dipole in San Jose Gulf. Being initialized with horizontally constant density, the model is also able to capture the oberved structure and intensity of main thermal fronts in the outer shelf and inside San Matias Gulf
URI: http://hdl.handle.net/1834/3877
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