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Oceanographic studies around the North West Cape, Western Australia

Posted on 07 October 2011

TitleOceanographic studies around the North West Cape, Western Australia
Publication TypeThesis
Year of Publication2002
AuthorsVerspecht, F
AdvisorPattiaratchi, C
Academic DepartmentEnvironmental Engineering
DegreeBachelor of Engineering
Number of Pages1-118
Date Published11/2002
UniversityThe University of Western Australia
KeywordsNingaloo, oceanography
AbstractOceanographic studies were conducted on an expedition around the North West Cape, Western Australia aboard the AIMS research vessel Cape Ferguson. A conductivity temperature-depth profiler was used to complete a transect through the entrance of the Gulf to define the density, temperature, salinity, chlorophyll a and irradiance. The profiler was also moored to the research vessel to examine the water structure in that position with time. Eulerian measurements were obtained using an InterOcean S4 vector averaging current meter and an acoustic Doppler current profiler. Lagrangian studies were conducted around the Cape investigating convergence through the use of drogued-drifters. The drifter results were plotted as current speeds, analysed for dispersion as a cluster and the difference between surface and deep drogue movement was investigated. The results of the dispersion calculations were compared to the results of the oceanic diffusion studies of Okubo (1974). The oceanographic picture that emerges around the arid North West Cape is of a region dominated by strong localised tidal currents. The deeper waters outside the Gulf are stratified in temperature while the waters inside the Gulf are vertically well mixed, more turbid and higher in chlorophyll a. The strong current system into the Gulf drives the mixing between the stratified water mass and the vertically mixed waters enhancing the productivity at the entrance. The frontal system manifests as surface expressions around Point Murat, along the boundary of the two water masses where the tidal currents are strongest and this slick of plankton attracts higher order species to the front feeding on the abundant prey. The dispersion coefficients are found to be low, but are considered acceptable, as this range is used in numerical models. Secondary circulation is observed to push the surface waters offshore causing the deeper waters to move towards the coast as a replacement, hence upwelling colder, nutrient rich water at the tips of the Cape. This transverse velocity is approximately 37.9% of the streamwise velocity and the flow regime is a balance between inertia and centrifugal forces. Instabilities are present in the wake of the headland at Point Murat during the strongest tides. This is evident from the drifters and from calculation of the Island Wake Parameter. The region around Point Murat is considered most sensitive due to these eddy-like rotations and the accumulation of particles, therefore numerical modeling is suggested as a further investigation into the dynamics of the circulation around the North West Cape.
Refereed DesignationUnknown
Verspecht Bachelor thesis 2002.pdf4.12 MB