Date Awarded

1997

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Advisor

John M. Brubaker

Abstract

The Northern North Sea and the Patagonian Shelf have similar characteristics, and their circulation is determined by strong tidal regimes, significant wind-driven flow, and by density gradients to a lesser degree. The influence of oceanic currents is notable in the Patagonian Shelf, where the Falkland Current flows along the shelf edge, but less important in the North Sea. While the North Sea is perhaps the most studied body of water in the world, the circulation of the Patagonian Shelf have remained fairly unknown. This study presents evidence of near-inertial oscillations in the Northern North Sea, not reported previously, derived from measurements with high vertical resolution in the presence of the seasonal thermocline. Data mainly from ADCPs and thermistor strings were processed and analysed, leading to the conclusion that the structure of these oscillations corresponds to the first baroclinic mode. Computations of the Richardson number suggest that mixing occurred during storm events, which caused the oscillations and hence an enhanced shear at the thermocline. Given the lack of direct observations on the Patagonian Shelf, its circulation was studied by means of numerical modeling. A three-dimensional (3D) model, originally developed for the North Sea, was adapted and implemented to the Patagonian Shelf. The model is barotropic and is based on a two-dimensional (2D) vertically integrated tide/surge model, with the expansion in the vertical following a functional approach with an eddy viscosity closure related to the flow. The model can be run as 2D or 3D, and for most cases here it was run as 2D, except when it was used to describe the tidal flow near headlands. Semidiurnal tides with standing wave resonance were found to dominate, while diurnal tides exhibited topographically enhanced currents. The simulation of the Falkand Current showed large influence on the shelf circulation, and the response of the shelf to the passage of low pressure centers generated surges and substantial wind-driven currents with clearly defined patterns.

DOI

https://dx.doi.org/doi:10.25773/v5-vs1v-2j94

Rights

© The Author

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