Wind driven circulation in Trinity and Conception Bays

Davidson, Fraser J.M. (1999) Wind driven circulation in Trinity and Conception Bays. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

In this thesis the wind driven circulation of Trinity and Conception Bays is described. I make use of three numerical models, ranging from a linear, single-layer, reduced-gravity model to the 3-D eddy resolving CAXDIE model. The CAXDIE model is verified by applying it to a lake initially at rest with horizontally uniform stratification, a parabolic bottom profile, adiabatic boundary conditions and no external forcing of any kind. Over time, vertical mixing of the thermocline gives rise to horizontal density gradients and cyclonic circulation in the lake. The models are then applied to investigate mechanisms that lead to observed asymmetry in the response of Trinity and Conception Bays to steady wind forcing directed out of the bay. I investigate the influence of factors such as continuous stratification, vertical mixing, nonlinearity and realistic bottom topography. Adding non-linearity allows for significant cross-bay transport of upwelled water and leads to an along-bay pattern of the surface isotherms evident in observations, and can also lead to the separation of the coastal jet from the upwelling favourable shore. The response to variable wind is also investigated and the modelling effort is compared to available oceanographic observations of the two bays including ADCP, current meter moorings, thermistor chains. SST and CODAR data. Overall I find reasonable to good agreement with the data. Adding the non-linear terms to the CAXDIE model improves the reproduction of observed thermocline movement. An application to particle advection is undertaken, which suggests that there may be little exchange of fish larvae between Trinity and Conception Bays.

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