Patrones hidrológicos y variabilidad temporal de la circulación oceánica en la región plataforma/talud del golfo Ártabro, noroeste de Galicia
This paper presents an analysis of data related to the hydrology and currents in the Gulf of ártabro -a region located in the north-western corner of the Galician coast- that were collected from May to September, 1996. The work has been divided into two broad sections; the first of which examines th...
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| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2008 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/316348 |
| Acceso en línea: | http://hdl.handle.net/10261/316348 |
| Access Level: | acceso abierto |
| Palabra clave: | Medio Marino Golfo Ártabro noroeste de España hidrología afloramiento filamentos marea interna ondas de inercia |
| Sumario: | This paper presents an analysis of data related to the hydrology and currents in the Gulf of ártabro -a region located in the north-western corner of the Galician coast- that were collected from May to September, 1996. The work has been divided into two broad sections; the first of which examines the data collected during two different oceanographic surveys carried out in May and September, in an area covering some 30 ˟ 35 nautical miles, while the second section analyzes the time series of data collected by means of two lines moored outside the area sampled. The first dataset was subjected to a quasi-synoptic analysis (the data collection took place within a timeframe of roughly 5 days), of the distribution of the water masses in the region and their dynamics, based on geostrophic calculations. This is the first comprehensive description of the oceanography in this region. Moreover, since the information comes from two different time periods -one at the beginning and the other in the middle of the upwelling season- it was possible to investigate the variability of the circulation patterns. The most important differences were observed in the upper-layer circulation, ranging from a situation in which the Poleward Current (May, 1996) was still distinguishable, to another one which led to the identification of the basic characteristics of seasonal upwelling episodes in the eastern contours of the subtropical gyres of the large ocean basins. In September, 1996, the upwelling was in a stage of (almost) maximum activity, and hydrological sampling enabled us to identify a structure with filament features emanating from Cape San Adrián (the most rugged topography of the coast in this area), towards the open sea. Minor changes were also observed in the circulation of the vein of Mediterranean water. With the time series, it was possible to examine the variability of the dynamics on different time scales. The most important was found to be the one associated with the tides that exhibit an intense baroclinic mode contribution, with large internal fluctuations and, more interestingly, a marked increase in the intensity of the bottom currents. Detailed analysis of the data collected would suggest that this increase is a consequence of the total reflection of the energy transported by the internal tide, as it hits the continental slope with its supercritical topographic inclination. The recordings of the currents also helped to indentify a less intense inertial wave activity, associated with the passage of strong atmospheric fronts and the transfer of inertial energy contained in the wind field. The most important inertial episodes coincide with pronounced changes in the sub-inertial velocity field, which has led to the hypothesis that the two phenomena might be related. At a lower frequency, the near-surface currents recorded would appear to indicate the regular formation of filaments in the vicinity of Cape San Adrián, insofar as the deepest currents show large fluctuations (tens, or even up to a hundred, meters), in the depth at which the core of the Mediterranean water flows. A curious relationship was noted between the alternation of energy episodes in the near-surface and the deep layers. This relationship has not been studied in this paper. |
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